My first father in law never paid for razor blades. He received blades in the mail from Gillette. Some kind of Shaving Team thing.
Here's the twist. He had to use the same blade for X-amount of time and record how well the blade shaved. It was my understanding that even if a blade was pulling at say day 5 and he had to evaluate for 7 days he had to just endure the discomfort.