Know the feeling. In the past (in fact last week) I had to conceal my new bass in the car until such a time as she was out of earshot upon whence I pulled the box into the garage where I quietly unboxed my quarry.
Later I sneaked it into the house where, once in the 'man cave', it received not a mention or glance.
Then she found the box in the garage!
Nah she's OK with it really, she's never begrudged my spending but I still hide things like that because I feel embarrassed I guess. Especially when I know she spends an awful lot of her hard earned on our little boy.