TROUBLE WITH VX - SHOP SALES

I'm having a bit of trouble with VX. Every time I go to buy or sell something from/to a shop it's set at $0. I've re-entered the cost amounts, fiddled with the scripts I was using (Yanfly's Shop, Shop variable costs, Beastiary and item description scripts - there were others but they didn't mess with costs or items), readded the scripts, deleted the scripts, closed the program and readded them again but I can't seem to find what the problem is or where it originated.
It must be part of those scripts, but I can't find what's doing it! I also tried the scripts in a dummy project, but they're working fine.

Any ideas?