I should clarify as well, I don't know whether this was a budget for the whole outfit or just the suit, I just made an assumption. The point I was really going for, and perhaps didn't properly convey was this: There is one reason and one reason only I spent a full $1k on my tux and that was that the Zegna outlet had $2,500 tuxedos for that price and I couldn't pass it up. Absent that kind of deal, I would have gone with the least expensive "proper" alternative available (I don't wear it often) and would much more readily have bought one at MSRP for $300 than $800-1k.
Were I buying today and an outlet trip proved fruitless/couldn't be done I would probably parse out $1k as follows (assuming it's for the whole outfit):
Suit: H&M, $270 + tailoring to remove belt loops/sew up vent so call it $325 all-in.
Shirt: If MTM can be had for $200, by all means. Otherwise I'd go as cheap as possible in the style you like (shirts can get ruined easily and the only part that matters is the bib since it's all that will be seen, so let's say $100.
Tie/Cummerbund: $235 will get you a good set from Ben Silver. I'd go cummerbund in case you don't have the belt loops removed from the trousers and need to cover them.
Shoes: I'd wear black calf that I already own.
That leaves a few hundred for a stud set which you will have forever. That's the part I'd spend the most on since it's the only part likely to last a good many years and stay in great shape.
No wonder why these days there is a lack of black tie event
I do agree the above is the way to go for a limited budget, I hope OP is young so the H&M cut would not look outer space for him
With the extra money I would at least try to buy a pair of velvet slipper or cheap ass patent leather shoe, wearing black calf to black tie is pretty much a sin. I much prefer a black waistcoat to be purchased in H&M to substitute the Ben Sherman cummerbund, there should be some good bow tie (the real ones that you need to tie yourself) on eBay