I'm thinking of scamming a company out of $500 of something that costs $1000
Why would you scam a company?
I'm going to take $500 from them by lying about something I've purchased
It's not right to steal from a company. You could get in trouble with the law.
I know, but I need the money more than they do.
There is no reason to risk getting in trouble over this. Paying for it in full is the best thing to do, stealing is wrong.