The good news is if they're taking a split of the revenue with you then at least when they say "Let's lower the price!" they also have skin in the game.
50 - 70% may seem like a lot. If you really only think you'll do a one time sale and not repeat sales then it might be too high. However, I assume that if you have a good service or offering that you'll get future repeat sales? So it's a marketing expense to capture a customer and the more confident you feel around the "lifetime value" of a customer the more you might be ok with such a big up front or initial revenue share cost.
50 - 70% may seem like a lot. If you really only think you'll do a one time sale and not repeat sales then it might be too high. However, I assume that if you have a good service or offering that you'll get future repeat sales? So it's a marketing expense to capture a customer and the more confident you feel around the "lifetime value" of a customer the more you might be ok with such a big up front or initial revenue share cost.