Perhaps the easiest way to avoid suit is to set your minimum price up front, say $10. Split test the prices up the funnel, but on the actual signup page, only

Perhaps the easiest way to avoid suit is to set your minimum price up front, say $10. Split test the prices up the funnel, but on the actual signup page, only charge $10. Nobody can sue you for price discrimination, and you can track how far down the funnel people make it at various price points. Once you have the information you want, you can raise your prices across the board.