I am a collector at heart, and that can cost me some cash... but when you are trying to complete a set, and buy 6 packs of cards and you walk away with 120 crystals... enough to buy another pack... that stings.

I don't like the idea of being crystals in this situation, its an insulting ratio, especially to someone feeding your platform a lot of money on a regular basis.

Some suggestions that seem reasonable:

1. Reward a random, unobtained rare from any set that you don't have 4x of already (get a rare for a rare, get a mythic for a mythic). This will help promote people completing their sets.
2. Reward a Rare/Mythic wild card token
3. Credit the "Gold Pack" progress count by 1 pack for rare and 2 packs for mythic.