Last I had a real cap I was an 11 at best on a very flat, relatively easy, muni course. We usually tell people you will run 10 shots +- better on the sim.
Assuming you have an indoor space with 9-10' ceilings & a decent gaming PC, you would need...
GC2 - $5400 refurb, ~$4200 used
Projector - ~$800-1000 (you'll want a short throw, Optima & BenQ seem to be the go-to's, I have a BenQ 1085ST)
Mat - $600 (Fiberbuilt, TruStrike or Divot Action) (don't waste your time and all this money and then get a crap mat, it effects every shot on your new multi thousand dollar toy) These are the 3 that are kind on your wrists
Screen & Framing - ~$400
JNPG - $35 on Steam
JNPG 1 yr. SimPass - $250 (annual reoccurring cost)
...so yeah, $7500-8000. There are definitely some things you can do to reduce...or increase...the cost.
For example, you can build a frame for the mat and just get a hitting 'insert' (typically 4'x1') and some turf for the stance portion for probably $200.
And you don't even need a screen/projector. We had a guy that took a net outside and used a monitor/laptop for the game for a year until he bought a house...
Then of course you can always increase by decking out the space with curtains, turf, putting area, stuff like that.
Im my case, I am outdoors in a 10x10x26' cage covered with a waterproof canvas tarp. Ran me around $1k I think. Damn tarp was expensive...
...and then if your really need to watch the budget, you can go with a SkyTrak over the GC2. It runs $2k and will cost an additional $100 per year gouging from SkyGolf, but it is a very acceptable unit. Plenty of them on tour including the tour winner on the NET side this year. But it can drive some people crazy also with the 'quirks'.