Only four times where it's acceptable to lie to your wife:
- No honey, you're not getting fat.
- Dinner tasted great.
- You're not getting old.
- She's not prettier than you.
Neither of us have to justify any purchases to each other. We have our budget and get paid into and pay out of our joint account for everything, and our own jobs that pay pretty much equal, both have jobs with pension plans and have our own 401k accounts we put into each payday that we never even see. All bills are paid before we buy a single thing, we're both very sensible in what we buy afterwards, extra money at the end of the pay period is set aside for additional savings (that are all pre-designated for their outcome as well), repeat next paycheck.
The only hidden purchases from each other involve gifts they will eventually know about anyhow. Shit, I've told her I'm saving for gun shit when really I'm saving for a big ticket jewelry item for her, because the first one I don't get the stink-eye for spending a lot of money on, but the second I do.
Honesty and communication go a very long ways in any relationship, and diamonds always boomerang back into high end optics.