Money talks and cash speaks the loudest, so when you’re talking to a vendor or the reception hall, ask them if they offer any sort of discount for paying with cash and most places, if they aren’t huge outfits like a Marriott or a Sheraton, they will offer a bit of a discount.
Why are they willing to do this? Well, with a credit card they have to pay interchange processing fees which can run somewhere in the neighborhood of 3% – cash has no associated fee. If you pay with a check, while there are no fees, there’s always the risk that the check will bounce – cash won’t bounce.