If you are buying gold or silver bars or current coins from the mint, you pay the spot price + whatever premium the seller wants.
I have purchased silver 1oz Pamp bars from APMEX.com. You can also find out the current spot prices for gold and silver.
If you are looking for gold/silver coins, take a look at PCGS.com and look under the Price Guide.
I have also bought some gold/silver on ebay. Just make sure you check out the seller's feedback. Example, I bought a 1795 silver dollar, off-center bust from ebay 5 years ago at $3K. Although not officially graded, it appears to be an XF 40 (extra fine above average) and possibly worth 10K.
