I find that when I offer to pay cash instead of putting the payment on my credit card, the vendor almost always agrees to a discount. They have to pay a fee of maybe 3% for the credit. When I ordered my $11,000. Scott Kay engagement ring semi-mount and wedding ring, they gave me a discount of 20% and offered to pay the taxes on the purchase - a huge difference in price! I also got a discount for my diamond by paying in cash.
Just a note about cash deals. If you do a deal for more thank $10k in cash, there’s an IRS/Homeland Security form that the jeweler is going to require you to fill out. Don’t take it personally, they’re required by law to do this.