OMG- I would be furious if my husband did this. I don't want gear- and it seems the OP's wife doesn't either. They've been on a trip and have another planned and she wants to rent; it seems to be an informed decision that she's happy using rental gear. Why should he override her decision, at significant expense?
I think every diver that really wants to get good and comfortable should purchase gear. I think owning your own gear has MANY more benefits than drawbacks or cost.
However, I had a rational discussion with my wife about buying her her own gear. She agreed, but only because we found a good deal on used gear. Even with cheap, used gear she started seeing the benefits of it. I've slowly upgraded her out of it, and she now owns a drysuit, two wetsuits, computer, 3 BCD's, a nice reg set, 4 sets of fins, 2 booties, 2 knives, 2 lights, etc.....and she's VERY happy with having her own gear. She even dragged it to and from our Mexico honeymoon with me. She even encourage me to get an O2 and CO analyzer, and an O2 bottle/reg.
I think the crucial element to purchasing gear, and being happy with it, is the timing of the purchase. Skittles, I don't blame you at all for not wanting your own gear. Let's talk about it again in 30 dives. Well, in Iowa that might not change. Well, what if you move to NC so close to wrecks? Or FL? Have you considered a PARTIAL gear purchase (like, just a computer)? I'm not saying you need to, but you need to buy it when the time is right. TS&M purchased gear before she knew what she wanted, and was unhappy with it. I waited 9 years after cert to purchase my own gear, and it was because I had just started diving locally and was on track to get my tech cert (I also had employee discount at the LDS). I was happy with my purchase. The one thing not enough people on this board discuss is WHEN to buy gear. The answer is: When you're ready. That's independant of whether or not you THINK you're ready.