When we married 38 years ago we agreed that one of us would not spend over a certain amount without consulting the other. It has worked well for us all this time. Such an arrangement also allows for a "cooling off" period and discourages large impulse purchases, and makes one consider if the purchase is really worth the discussion, from a timing stand point if no other.
While she questions if any item as mundane as a razor or shaving brush could possibly be worth $300, there have been items she wanted that I've questioned also.
We have shared "doing the books". At one time I was traveling alot and she took over. Later when she was too busy, or just tired of it, I took care of the money. Most of the banking is now on line, and as I have better computer skills I now handle the money. Lots of ways to skin the cat.
She does think I'm a bit nuts for shaving with a straight razor. On the other hand she tells all her friends, so I know there is no hidden resentment.