I have an old Norinco rifle box in the garage. She thinks it's there because I'm saving it for when I sell a gun and need a box to ship it in... I time my purchases so I know she's working nights and sleeping. I pull my truck into the garage and offload the new gun into the Norinco box. A few hours later when she leaves for a night shift I move it from the garage to the safe. This way I can avoid the doorbell camera and the 1,000 questions.
Thankfully once it's in the house she really can't tell what is new and what is old. I occasionally get the question "Is that a new gun!?" when packing up for the range and I just laugh and tell her she's paranoid.
With the amount she spends on yoga and the amount of receipts from clothes stores I find on her dresser, I don't feel bad lol. It isn't really a money issue it's more of a "why do you need so many different guns, don't they all do the same thing?" thing.