Should I let them go?

First off, I hope this is the right section as it seemed most appropriate. So I'm going to cut through all the backstory and get right to it. I'm currently negotiating a trade, websites/domains for services.

Here are the sites/domains:


Here are the proposed services, quoted directly from the person:

If you want to trade my list here for the 3 sites I will be much obliged to continue assisting you with the rest of the sites past the 1 page you indicated, and continue until they are ready for marketing which I will assist with at a 'retail value' of about 475 per each of your 3 sites. This would mean writing some content/ads, social marketing, some link building, maybe a press release or two, virtual property deployment for link satellites added and serp listings, along with cross promotion from my sites and partners.

Click to expand...

I'm not sure how to proceed here. I feel like these are some of my most valuable sites/domains yet the 3 sites that I would have developed would definitely be a big step towards my actual project to which none of the above domains relate. Should I let the sites/domains go for the bigger picture or is there some real gems here that I should hold onto?