Nice stuff. Personally I would love to see some Pain Killer type sound tracks. Makes me want to go out and frag someone. 
The thing about marketing and setting a price has nothing to do with what you might think your work is worth but what the free market is willing to spend based on options made available as well as branding.
If you were John Williams you could set your price to almost anything and people will buy it.
But trying to be helpful no one knows how big the marketplace is as far as individuals who have access to it through subscription, and I doubt Epic will tell you, or what prices will be as to products that will be similar to yours.
To figure this out there are two things you might want to do at this stage.
- Wait to see if similar products comes to market and see what their prices will be. I suspect that there will be a lot of price adjustments being made in the first while as the marketplace balances it’s self out.
- Market a test flier.
A test flier is a simple constructed product intended to test the depth of the market based on volume of sales calculated against the rate of return.
Simple idea. You sell something for a buck, and since Epic has to pay you, this will tell you just how dynamic the marketplace is with out having to know the total number of subscribers.
If you can figure out those two setting your market price is an after though and the only consideration is the hours of work worth the rate of return?