I used to have a buddy that did this with guns. He'd buy new ones and tell his wife he was "selling" some of his others. He'd list them for stupid high prices so they never sold. He's divorced now.....go figure.
Myself, I don't keep anything from my wife. She likes different things than me. It used to bother me how much she'd spend eating out at restaurants. It used to bother her how much I spent on guns, knives, and tools. We just have different priorities. Now we operate on an "allowance" system. Figured out we both spent about the same, just on different things. Now she could care less what I buy with my chunk of cash, and I'm the same.
But regardless, no need to lie or sneak stuff by your wife. For the most part, they're smarter than you are in that regard, and they know what you're doing. Put your marriage first, and come up with something that works for the both of you. Be resourceful and work together like a team.