I know you've said that 20$ isn't actually what you want to price your armor sets at, but I don't think you realize how bad that looks.
Let's look at WarFrame for comparison, and we must because that's the market you're tapping into and likely the biggest competitor you will be measured against.
I bought a REALLY nice skin for one of my frames off their store, a tennogen workshop creation and it only cost me SIX DOLLARS.
Skins are the warframe equivalent of your "armor packs". If you're charging anywhere above 8 dollars for them you are going to LOSE and that is simply THAT.