Continue doing what you are doing. The higher up the rankings you go, the longer it takes and the harder it is.
One thing to think about though is the keywords you are targeting. You should be getting quite a few sales at #5 if the keywords are correct, especially for a search term with a monthly search volume of 22k per month. As a general rule, #1 will get roughly half the search traffic and the percentage of search traffic roughly goes down evenly to #10 which receives about 3% of the search traffic. You should therefore be receiving a high volume of traffic already, and if your site is reasonable, a high number of sales (certainly more than $12!)
Perhaps modify your meta description to improve CTRs and think about the position of your call to actions, their colour etc. to improve conversions
Right, I don't know what made me think 22,000, it's actually 6,600 monthly for this keyword. I chose it because it appeared to be fairly easy competition, but it hasn't turned out that way.
Can I even make back my $1,000 investment with this keyword in the top spot?
The #1 spot is currently held by AsSeenOnTV, but they don't even have the keyword anywhere, they just happen to have both words on the page separately.