What you need is an option to specify QTY breaks.

List up as many or as little as you want.

Set price break for item..
QTY: 1 = $49g
QTY: 10+ = $45g
QTY: 99+ = $41g

When said purchaser comes along they can enter how many they are looking to buy and be offered the amount in separate lists.

This way if the supplier lists a minimum break of 99+ it means that it can only be purchased in stacks, however they could list the whole stack with a QTY break of 1 which would allow people to shave off the top. If a few people shave they could still get some savings buy buying 10+ or 20+ whatever you set it to.