If you are a bit patient, and live in the US, you can make your $50 price point by waiting for the basic Kindle model to go on sale. Sometimes (not now) Amazon has it on sale, and sometimes you can find it on sale at an office supply store.
You also could make your price point by purchasing an original Kindle in like-new condition as an Amazon warehouse deal for $48.26. They are slapping a
no warranty notice on it, which probably means 90 days. If you watch the
Amazon Warehouse Deals web page, you may find something newer in a few days -- their selection tonight is not the best.
You are fairly safe with no warranty if you are gentle with your possessions. But the great thing about their eInk Kindle warranty, for the rest of us, is that they have historically honored it even in case of screen cracking.
Note that the United States is the only country where public libraries commonly lend eBooks in the Kindle format.