The dream is that you'll turn a good percentage of those amazon shoppers into full-price return customers where you're not sharing percentages with amazon. Why are people buying services with amazon though? They like one-click buying, with amazon's guarantee of no question you don't pay if you're not happy. amazon also makes it easy to leave feedback, so you're going to have to really excel, at a discounted rate, to avoid being trashed when a spot doesn't come out. Could work out great if you're set up to handle it, but I'd guess the lowest price will win and there will be a lot of churn in their service providers.
BTW in Seattle there are already three companies and amazon wants more, so I'm not sure how exclusive they are in every city.