I am not that good with price ranges so i will leave recommending mainboard part to wiser people here. But i would like to remind "many" mainboards does not support FX cpus with "default bios", if you happen to buy one of those be sure to ask them update bios before installing your cpu, unless you already have non-fx cpu to update it.
Depends what you mean by inexpensive.
I think $100 is inexpensive for a mobo.
Plenty of boards for that price with the latest features and FX cpu support.
You can go cheaper but will be limited to 8gb of ram and less features.