Today, there is not an option for "variable" pricing. We have "variable" pricing on our customer request list and may be able to support it someday, but for now, you can try one of the options below.
Each item does need to have a price that's already configured in the system, but there are a few workarounds you can set up:
1) Enter items called "Other" and create one for every possible price point that you may sell these items for
2) Create just one item with the highest price point you may sell these items for, and apply a discount with each transaction
If you go with #2, you'll want to set up a transaction-level discount reason to track why a discount was applied. Here's a helpful article about discounts in general: Setting up discounts