Step 1) buy $100 gun from:
http://www.jgsales.com/product_info.php/p/feg-pa-63-pistol%2C-9x18-caliber%2C-vg-to-excellent-/products_id/1258
Step 2) sell $100 to police for $250
Step 3) profit!
More like a $175 gun--at least around here--once shipping and FFL handling fees are taken into account. Further, non-FFL's are not allowed to sell guns purchased for the purpose of resale.
BTW, I wonder why the quoted shipping for three guns is more than twice as expensive as shipping for two.