I think I read an ancient article from Joel Spolsky (?) about this once. Basically if you're going to charge different prices for the same product (the context

I think I read an ancient article from Joel Spolsky (?) about this once. Basically if you're going to charge different prices for the same product (the context was A/B testing price), you could marginally change the product so that there's no real difference, but at least they're not exactly identical. It would circumvent the question you're having if you're not sure about the legality, because they'd be different products legally. There's no law that says you can't not sell something. If your product is software/SaaS, it's very easy to do this: allow 101 actions per month instead of 100, offer longer trial, change the colours/interface, offer longer money-back-guarantee, ... Of course be careful that these changes themselves don't skew the A/B testing.