:: jumps into the pond ::
Beauty is in the eye of the beholder.
We should clarify some terminology.
A domain is a unique alphanumeric address used for locating Internet Protocol addresses (paraphrased from ICANN's "Beginner's Guide to Domain Names"). A purpose of an internet domain is to have a memorable name. Domains are leased, generally on a yearly basis. Domains are leased through domain registrars. (For this post I am blanketing the cost to register a domain at $10 per year.)
A website is a file or a collection of files made available to visitors of a domain, usually navigated through a web server of some type. A website usually has costs with it associated for use of the web server, and any other types of resources utilized for the website; these are called web hosting costs. Web hosting costs are generally on a monthly basis. Websites are hosted through web hosts or web hosting sites.
Any domain is worthless until you find a buyer.
Because all domains are leased, they cannot be purchased. However, the lease can be purchased. For some stupid reason it is common for people to say they "own" a specific domain, when in reality they only "own" the lease to that domain. I make this stupid mistake as well.
So, when you are trying to sell internet domains, you are not selling the domain, per se, but the lease for that domain. Here is an example:
You "buy a domain" for $10. It is worth $10 or -$10 to you, depending on how you look at it. You have really purchased the lease to use that domain for one year. If you do nothing else, then in one year that lease will expire and you will no longer "own" that domain. If you wanted to sell your lease to that domain, or to sell that domain, then you should try to get your money out of it and ask for at least $10. And here is where we get into craziness.
If the domain you are trying to sell has a name that is truly memorable then it may have value within the realm of marketing. When I say, "memorable," it could be memorable for whatever reason. XKCD.com is memorable because the artist behind it is a genius. Coke.com is memorable because of the insane amounts of money Coca-Cola has spent on marketing that word. (Funny thing though is that right now, coke.com redirects to coca-cola.com.) Nike.com is memorable because of the marketing done by Nike. Your website, rvparks.net is a memorable name, however, to whom? I have never bought a coke product from coke.com or coca-cola.com, but I know I will see their stuff if I were to visit that site. I can easily imagine if I were to visit rvparks.net that I would most likely find something having to do with recreational vehicle parks. Because of this, it is memorable. Also, if you want to use the keywords "rv park" or "rv parks" you have a great domain.
If the domain you are trying to sell does not have a memorable name then it is still $10 to lease it each year. If you purchased the lease on a domain for $1,000, then *you* may believe it is worth $1,000 because at the moment you purchased it you most likely believed it was "worth" $1,000. Remember I said that, "any domain is worthless until you find a buyer"? Well, whoever sold you that domain can truly say it was worth $1,000 when they sold it to you because they were able to exchange the lease for that domain, which may have cost them $10, for $1,000 from you. If they did originally spend $10 to register that domain, was it worth $1,000 when they originally leased it? Or, was it just worth $10? So, if you spent $1,000 on a domain, but you are unable to sell it for $1,000 or more, how much is the domain worth? If you eventually renew the lease on that domain, you have to spend an additional $10 to renew it, so now, *you* could argue that it is worth $1,010 but whether you convince anyone else of this or not is the challenge.
Worth means, equivalent in value to the sum or specified item (*google).
If I purchase an oil painting for $400, that does not mean the materials used to create the art total to $400. Most likely, the material cost around $60! The artist slapped a price on their name and labor of $340 and added their material costs for a price of $400. Does that mean the painting is worth $400? Blah, art is such a stupid finance game, but for the sake of example you can see that the material costs are $40 and the perceived value addition of $340 is acceptable so paying $400 may seem reasonable. However, if someone else were to see that same exact painting they may not be willing to pay $20 for the piece! How much is the painting worth?
In business, we try to create wealth. That is a large portion of business. We purchase goods and we sell them for more than what we paid. We value our time and skills and we sell them as a service for whatever value we perceive them to be. If you were to meet me in person and ask me to provide you with advice on a current project of yours, I would tell you that I charge anywhere from $200 to $1,000 an hour, depending on availability and requirements. You may decide that price acceptable or unacceptable. Now a nuance of the word worth is that after you hire me at an agreed upon rate, you may believe that cost to be either worth it or not worth it. Having that hindsight is great, but before you hired me in this example, if someone were to ask you how much am i worth per hour, what is the answer?
rvparks.net is a great domain if you are willing to find the buyers who agree with that idea. If you are just trying to flip the domain, and waiting for someone to find you in order to close the sale, then you are probably not going to make a lot on it. If you are willing to put some time into it and find the right buyer for it, then you have a better chance of making more on it.
When I search for "rv parks in the us" the number one result is from travelchannel.com. The title for their #1 result is "America's Best RV Parks". The #2 result is some page from campendium.com which just has a self-proclaimed guide to RV Parks. (***SIDE NOTE: If you are into flipping domains, pay for a web hosting service which allows you to create as many new websites as you want for a set price. There are plenty from which to choose.) Based on how lame these pages are, I would propose you NOT sell the domain right away. Instead, I propose you create a website that has some good useful content on it, and capture as many RV Park related pieces of information and share them in a logical and clean manner on your site. This will allow you to sell advertising space on your site, be it to direct advertisers or Google AdWords, or whomever. My guess is you could probably make your money back in the first year with minimal effort. Then, should you choose to sell later, you have more perceived value to offer. BTW, it is completely reasonable to sell a domain and a website separately ... so let's say you do build up the domain's perceived value by creating a high-traffic website on it, then you could sell the domain alone for $3,000 or the domain and the website for $5,000.

You sell for more than what you paid and walk away knowing the investment was worth it or not.