Six months ago I launched a free app that I developed and self-funded. From peak usage of a few thousand users, it has now bottomed out at a few hundred. It was an interesting project, from which I learned a lot, but I was never profitable and am now looking to discontinue service or sell it. The main driver for not just leaving it in the app store is 1) back-end hosting costs and 2) un-patched security vulnerabilities.
In my situation, what is proper procedure to deprecate the entire app?
How would this change if it were a paid app?