Keep most of your old camera equipment and be very disorganized. She will never notice as more parts are added to the 'pile'. Never let her see the money handling. Never explain what individual parts are for, she likely does not care anyway. Make a big deal of it when you sell old stuff on ebay, not mentioning that you are getting about 30% back from what you paid.
I remember when my wife let me buy my first DSLR setup. She said, "I am glad to do this for you so we do not have to buy any more camera equipment." They are so cute when they say things like that.
Lana Turner said it best
A successful man is one who makes more money than his wife can spend. A successful woman is one who can find such a man.
If you give her a lifestyle she is happy with, she is less likely to be unhappy with yours.
While presented in humor, you might find useful facts in there somewhere.