There are three possibilities. The first is that you are a complete pillock. The second is that you're married to the wrong woman. And the third is that you've bought into a myth about personal relationships, namely, the War Of The Sexes, where neither side ever makes allowances for the other's shortcomings. I sincerely hope it's the third.
If you lie to your wife about what you've bought (or she lies to you), because you can't afford it, you're heading for bankruptcy or divorce or both.
Except for the smallest purchases (under, say, $100), or purchases where we KNOW we're going to agree, we discuss it first: whether we can afford it, whether we need it, whether we even really want it.
Twenty-six years last June says we're doing something right...
Cheers,
R.