Bumpsale is an online service which allows you to sell your digital product while applying an incremental price that raises each time someone else buys. You decide how much is the "bump" in price everytime someone else buys. Each new potential buyer sees the price going up in real-time as other buyers make their purchases.
Each buyer has a maximum of five minutes to complete his purchase at the price he sees at any one moment.
Bumpsale works with Stripe (and soon with other merchant gateways like Paypal).
*I assume that Bumpsale keeps a commission on your total sales but from the info available on the site it is not clear how much that is.
See demo: http://demo.bumpsale.co/
Try it out now: http://bumpsale.co/