So imagine a small piece of UI, only several pixels tall/wide, that displays a product's info. Usually this widget shows either something like $0.99 USD, BUY, or FREE in order to convey that it is available for purchase. We now have a new use case in which we need to sell products using a "Pay What You Want" scheme, so I've been trying to figure out the best way to communicate this to the user without actually using a "Pay What You Want" label, which would be way too long for our current widget sizes.
So far I've only come up with "Donate" which is a bit inaccurate or switching to a small icon, although I don't think there is an icon that is universally recognised as Pay What You Want.