Re: Forge version 1.5.29
Yup, I believe I mentioned that somewhere along the line when updating the booster prices. These Fat Pack prices have been around to be exploited before I made the changes to correct the single booster prices -- it's just more evident now. Since there were no previous Fat Pack entries in the file yet they're still displayed in the Shop, I guess it's getting the value from somewhere else. I've had no insight so far, however. 
EDIT: In real values, Fat Packs tend to be priced higher than 10x the price of regular packs. For Quest Mode purposes, however, I feel like that would make little since since the availability of material in the shop or "novelty" value aggregated to these produts is not a factor. For that reason, I suppose a x10~ multiplier on regular booster prices would do the trick to fix these values for game purposes.
EDIT: In real values, Fat Packs tend to be priced higher than 10x the price of regular packs. For Quest Mode purposes, however, I feel like that would make little since since the availability of material in the shop or "novelty" value aggregated to these produts is not a factor. For that reason, I suppose a x10~ multiplier on regular booster prices would do the trick to fix these values for game purposes.