adsReloaded is all about getting downloads. Let's say you have a 0.99 cent app and decide you want to spend about $25 dollars on advertising. For paid apps the price you pay users is at least the price of the app (so for a 0.99 cent app the minimum payout to a user is 0.99).
Since your budget is about $25 dollars you take the CPD (cost per download = 0.99 in this case) and multiply it by the number of new users you want (let's say 20). This puts your total advertising purchase at $19.80. I take 25% (added to this number) + the price of one download (to moderate the campaign/test to make sure the question is correct). So the total campaign price for 20 users follows this equation: 19.80 + 4.95 (the 25% I take) + 0.99 (price of app) = $25.75
This $25.75 will get you 20 new users. Granted you will make back .70 cents per user so really it will cost you $25.75 - 14 (your profit) = $11.75 for 20 new users.
This may be murky brand awareness to you but I think there is also a "word of mouth" marketing piece here as well... and if you push it hard possibly even extra downloads from moving up the app ranking lists.
Does this help explain more?