i think if it's a reputable coin store, you wont be able to haggle much on the price.
i think if you pay in cash, you can probably get it cheaper... and if you buy a decent quanity, you can probably get sorta a bulk discount. they might knock off $20 off the total if you buy 5 ounces of gold instead of one... but i wouldn't expect any big discounts, espeically since the demand is so high.
and if you're buying silver eagles or something for example, and the spot price is $13... the coin store might charge between $18 and $20, that is, if they even have any eagles to sell. so if it's a reputable coin store, the price is the price. the paper prices don't matter when coin stores are all out of stock and demand is exploding. if you're not willing to pay the premiums, someone else will