I had a customer in the parking business years back. A private parking lot operator technically does not have the right to issue you a parking ticket for parking on their lot and not paying.
However, they do have the right to offer people who prepay a significant discount. So, if you pay up front, all day parking is $10.00. If you don't pay and they catch you, you get to pay the full parking rate of $80.00. This IS legal.
All this to say, I like the cash discount recommended by @JeffSchwenk . Pay me by direct deposit and I will give you a discount. Pay me by check or credit card, then do so without the discount.
If you have someone who is cheap and just wants the module, you are really in a straight retail transaction. The challenge is that Blythco will gladly take that transaction and run (picking up the ROR in the process.)