It appears that a quarter page ad is as low as $269 to as much as $333 per monthly issue.

Here is a link to the details:

http://www.money.org/AM/Template.cfm?Section=Numismatist&Template=/CM/ContentDisplay.cfm&ContentID=15859

However, it should be noted that these are "member" rates. I do not know if our affiliation to ANA (as a Member Club or whatever the appropriate designation is) allows these rates, but ANA Member rates are about 3% below their regular rates.

Jim