I will quickly add up my kinda cheap RB25/30DET conversion, its not quite finnished.
Not including the block and head which I pretty much got for free:
ACL Race rebuild kit, came with cast pistons, rings bearings gaskets etc, about $400 trade price at repco.
I got the head rebuilt and modified for VCT plus the block drilled for the extra tensioner that was about, the block bored and honed surfaces decked I think it was around $1300
550CC injectors $300 (pretty sure theyre out of a 95on VG30DETT)
We put the motor together ourselfs.
I am going to need a custom exhaust and I am going 3.5" (its going in a VL) I got a quote for $1000. I am going to use a cheap hyrbid cooler 600x300x76, Should cost around $600 with plumbing. JD plenum $600
I am getting near new GT35/40 .82ex and 38mm Tial gate for $1650
6Boost manifold $1200.
R33S1 Loom $50, Wolf3DV4 skyline plugin $650
Thats about $7700 theyre. You wouldnt need a JD plenum and 6boost manifld, or the $1000 exhaust, so I reckon you could almost do a 30DET for $5000 if you can do a lot of it yourself or with your mates and your conservative, use 2nd hand parts If all I had was 5k and thats it I wouldnt try as you can see I got some good deals, but im sure u can get a bit more cash, my cars been off the road for nearly a year now!
Anyway I hope its some indication.
If I have missed anything let me know and I will update it.
Cheers Eddie