"Read-mostly" is a use case where you're going to write to it very few times (maybe even just once) but read from it lots of times. For example, I have a stick with Windows 10 install files on it. So write performance is more or less immaterial but read performance is important.

Regarding price, I just set a threshold price at camelcamelcamel.com and buy one from Amazon when that threshold is met. The unfortunate side effect is that I have way too many of these