My friend's birthday is next week. While I was shopping for her, I saw a nifty cat toy that would help keep her cat entertained while she was at work. I then realized that my cats would also enjoy a toy like that. I want to buy one for each of us, but I am worried that that would somehow be bad form.
For myself in the UK, it's actually not a bad thing, if anything, think of it as "oh hey, I have this thing which is pretty amazing, you can have one too". I mean if they never find out you have one, then it can't be an issue anyway.
More so, if it is a good piece of equipment, then why shouldn't both of you have it? Not only do you have something else in common (i.e. both your cats do the same things with the same toys) but it can also be a conversation topic too ("How is your x doing with your cat?")
Of course if you live elsewhere then it might be best to see if someone from your region has better information ;)