From what I have seen you don't even need a 1k machine. It's very frugal, like most Half Life games. Well, especially on the Rift which doesn't have the biggest resolution of VR headsets. Apparently the mixed reality ones work fine too, though we have not seen the big discounts on those that the U.S has seen. They are frequently available for around $200, but sadly not here in the U.K.
I got my Lenovo for about £100 last year.