20% cut is a little stiff.
As they rightly point out in the benefits these aren't leads, they are closed sales.
It's high. They're not first to the scene. If you look at Elance, it's 8.75% for exactly the same thing including payment processing. On the high end, I've worked with agencies that charge 15% for everything. 20% is steep.
In some industries 20% is a money losing exercise.
They'll probably acquire more nuance eventually.
If Amazon provides leads but the service provider still does marketing, customer service, accounting, payments, sets prices, insures against fraud, closes the sales and so on, you'd expect Amazon's margin to be pretty slim as they're basically a telephone directory.
But if Amazon manages the customer relationship, does all the advertising and customer service, sets the prices, makes the final sale and all that, so the service provider just turns up to do the job, they could probably make a much better margin.
"Transaction fee includes all relevant fees for invoicing, payment processing, and fraud protection."
What is this? the 90's ? Anyone can set-up a simple free website and offer his services, of course a little bit of marketing and patience is still required, but for a smart man, that doesn't cost anything.
Amazon is the e-commerce juggernaut; Amazon.com is the 7th most popular website in the world. (4th in the U.S.)
The dominant player in a market sets the price. (apple & google play take 30%, uber & lyft take 20%, think amex/porsche/jetblue/nike...)