It comes with rack rails. It's $50 over your budget but it's one of, if not the best rackmount case available. In fact, there are a couple of DAW builders than use this exact case and just rebrand it. Rain Recording being one of them.
I think it's also a 4U design...which is more common than 3U, which is probably why 3U is more expensive. Supply and demand, man. I'd go 4U anyway. More breathing room.
I've got a 3U and I'll tell you why it's cheaper...........you can't find a replacement power supply!!
Mine still works, but I started looking a couple years ago for something a little quieter and soon found out it's impossible to find an ATX 3U power supply anywhere.
It looks like I should get a 4U case which sucks because I have a 6U rack with (1) Furman power conditioner & (2) Firepods already in there. I was originally planning on putting an Alesis HD24 in there, but those things are a little bit out of my price range.