Very interesting question! We've been at this toy thing for a very long time. Up until about a year ago 100% of them were for her. It was definitely my idea - if she thought of it, in those days she would have been too shy to mention it.
By the same token, I did not have to do much arm twisting to get her to go along. So the question is - did she have a desire - or was she just going along? I honestly don't know - but now I'm going to ask!
The other question is why did I do it? Thinking back - I was just your typical 30-something husband who wanted to have sex way more often than my wife. Having pretty much exhausted all of the advice for manual and oral stimulation - it was kind of a natural next step.
Lastly - your right - it does turn me on. The process of shopping, ordering, then introducing them to my wife is erotic for me. Since I travel a lot, I often create a card, print out the reviews - and get to her to try out the new toy while I'm on the road. When I get back I get a lesson on what works best!
Needless to say - she's come a long way baby!