I'm certainly not trying to say that every example is like this, but I also don't think it's fair to say that sellers can never consider fixed costs and that imperfect information makes the reasoning impossible.
Another interesting example is kickstarter. It provides goals at different levels, with different rewards at each level. The different levels in many cases are effectively providing price discrimination even though they may have marginal benefits. Some projects reach their goals and get funded only because people at different levels of interest choose to fund those projects different amounts. If they could only set a single "price" for all backers they would never happen.
Another interesting example is kickstarter. It provides goals at different levels, with different rewards at each level. The different levels in many cases are effectively providing price discrimination even though they may have marginal benefits. Some projects reach their goals and get funded only because people at different levels of interest choose to fund those projects different amounts. If they could only set a single "price" for all backers they would never happen.