[Miraste]

Valve Index $1k

Vive trackers $300

2080 Ti $1200 (I suppose I should count this by its new "low" price, but I got it early)

Overclocked i7-6700k and high end motherboard, closed loop cooler with better fans, ssds, psu, case, ram etc ~$1400

= ~$3900

The important parts are the Index, the 2080 Ti, and a CPU with high single-thread performance. If you lose the trackers (more trouble than they're worth, really) and go more budget on the other parts you can put together something equivalent for under $3000, but not by much.