I’ve just built a rocket for 3.5, I got the rp23 with a hope headset for £1550, save a hundred by getting the float
I could have saved money on each of the following parts without it effecting performance
Reverb £200 (I think you need this)
Sram xo rear mech £150 (could save £50 here)
Hope M4 brakes (special edition paint job) £270 (get slx and save £130)
wheels £300 (proabably save a £100 here)
XT crank £160 (Save £50 here)
100+50+130+100+50= 430
so can be done for about 3 grand with a reverb.
I got a £400 marzocchi fork from winstanleys, very good it is too
You could easily build one for 3 grand without compromising.