My build is similar. I also got a dell optiplex 7010, although I paid $80 for it on ebay. I got a fairly nice power supply (BitFenix BF-450G — got a good review on Tom’s Hardware) for $60, and an EVGA GTX 1060 3GB for $190. I was worried about getting the graphics card used — apparently ebay scams are not uncommon — you end up with a lower-end card with higher-end stickers. Also I worry about people overclocking their card, running it hot, reducing the lifespan of the card, and then selling it to me. So I went with new. That being said I’m jealous of OP’s GTX 2070. The graphics card I got is a single fan “mini” model that fits nicely in the optiplex 7010. I wanted a two-fan model, but I didn’t feel like grinding out the hard drive cage on the dell.
The GTX 1060 seems to be struggling a bit with the water simulation — the simulation looks fine, but I’m getting “out of time” errors on the console. I researched graphics cards a ton, and although I was worried about the limited RAM on the card I got, it looks like video RAM usage is minimal (under 100MB). I wonder if I can somehow tune things so it uses more VRAM and gets better performance on the water sim. I might downgrade to Mint 18.3 as OP suggested and see if that helps. I’ll also try downgrading the resolution.
The thing I did not really research as much as I should have is the projector. I got a cheap one — refurbished Nebula Mars Lite for $220. I set everything up and discovered that the projector does not have a zoom feature. I didn’t even realize you could get a projector without zoom. So now I’m messing with mirrors and have to deal with the projector creating its own shadow since I mounted it lower on the vertical post (pointing up to a mirror). The projector does have a threaded tripod socket, so mounting it is pretty easy. I wish I had used https://www.projectorcentral.com/projectors.cfm for comparing projectors, they have product specs and comparison tools.
Anyway here’s what the bill came out to:
Computer $80
PSU $60
GPU $190
Projector $220
Sandbox and equipment boom $200
Sand $170
Total $920
For a real budget build I probably would have gone with regular play sand, but it’s too cold outside to do the wash process.