Essentially, the Amazon field definitions allow you to specify “min” and “max” pricing fields under the Price mappings. However, these are simply bounds and we’re not sure how Amazon handles them. (Amazon’s documentation for Seller Central is quite lacking unfortunately – they don’t even provide a sandbox environment for developers to test on; we had to set up a live account.)
With respect to automated re-pricing, that was originally planned for an Amazon Phase 3. However, there was not much demand and we focused on eBay instead (for which there is even less demand, ironically!).
I’m afraid that means, for now, you would need to go with a third-party. Hard to say with online reviews, but there is a “top 10” here:
And this seems pretty legit:
Obviously, we’re not endorsing it and we haven’t tested it ourselves.
Let us know if there’s anything else we can do to help.