That doesn't answer the question at all.
Yes, it does.
Redbox you need to leave the house to get your movie, for Amazon's online rental service you don't and you can start streaming it immediately. Thus, some people will be willing to pay more for it. Plenty of people pay extra to have things delivered to their homes rather than going out and getting it themselves.
Redbox has a limited library because it all has to fit in the machine. If they don't carry it (and they don't carry much besides newer movies) you're forced to go to another service like Amazon who can charge more because you don't have as many other options. Less availability means higher prices.
There may be contractual reasons why they charge more, but even if they pay the same per movie as Redbox I would think Amazon would charge more just because they can. Their goal is to maximize their profits, if they see an opportunity to charge significantly more than their costs they'll take it.