Heya Aia.
Generally, about 30-35, some a little more...but it really depends on the module. The Keep on the Borderlands series (5 modules
iirc), Lost Tomo, Hommlet, or certain game day releases seem to be on the higher end. I got my Keep series in shrink for about 15 per, but that was a couple years back...I know the system may not be that desirable but man , the art ...I collect it just for those reasons! The rule books...now those things are utterly worthless
Have a great one!
Matt