As veeman siad, NEVER lie to your wife. Especially about the cost. More than once Ole Joe passes on and the widow sells the guns at a fraction of what they're worth because Ole Joe lied about their cost. In this case, I'd tell her that, "yes I promised for a year, but this just came up and it's a heck of a deal. What do you say I get this one because they don't come up at this price and condition very often." That is better than lying about buying a gun, or about the cost of a gun.
Dan
Dan