I have 3 flyable 250 class racers... they make it look easy... it isn't. I wouldn't even be able to fly in such a confined space for long.
Everyone in the FPV scene use Fatshark or SkyZone goggles, I'm using a Sony HMZ-T3W

I get a little lag, but much better rendition.
The actual quads a pretty cheap to build, but when you start adding up the FVP gear and repairs... it's not cheap.
You can get a good prebuilt for ~$500.
Last year I had an idea of streamed racing... but then I realized the US was already kind of doing it, I sucked at flying and hobbyshops don't have the money to make me rich.
I reckon in 10 years time drone racing's going to be really fun to watch... think Wipeout (PS game).