To me at least, $90 feels pretty affordable when it's something you know you'll be using for the next decade or so (that's how long my P180 lasted, so I'm planning on the same for this one).
Spent more on the Three Hundred, but still less than half of that $90 and it's done fine for eight years or so now. I don't think longevity is something I'm concerned about for cases. Build quality, air flow, ease to work with, and aesthetics all seem to have more range of values.
(And by all means that R5 looks to be great in all those areas. While the Blackhawk I picked up isn't obnoxious, it is not as clean looking as the R5. I sacrificed a bit on aesthetics and likely some on build quality as well. But, well, $18 is little enough to be nothing in terms of a PC budget. I could spend more than that on a single case fan.)