Tokens do trade for just a few sats up to many many thousands, there is no set standard for an exchange to delist, they still make money on the fees unless of course all the market activity ends, say on an announcement that further work on the protocols and standards are not to be continued, for instance. This development work is key to a digital tokens ongoing life and this is also the reason for the most popular of these being at such a good price per token.

Most of the times when an exchange announces a delisting, this is usually to do with the ending of a tokens development, sometimes even; the blockchain has problems, the exchange reaches out to the developers and with no response, there is no choice but to delist.

There are many other reasons too...