I just went through this and I know exactly what you are going through. I have spent the last year, trying to convince my wife that I needed a kamado Joe. She was dead set against it. I have an OTG and a WSM as well as a very nice gasser.
I worked some overtime to cover it out of non house funds and told her that I was going to buy it. She was upset, but I told her honestly that I don't golf, I don't smoke, I don't gamble and I am not a huge go out and blow cash kind of guy.
I told her that it was something that I really love doing but she really didn't see it the way that I did. But finally agreed that as long as the money didn't come out of house funds then so be it.
She is enjoying the food now more than ever. I BBQ at least 5 nights a week on it.
Something you can consider, and I think for me is the best reasoning is that it will probably be the last cooker you purhcase. Lifetime warranties and overall quality is unprecedented. I went with the Big Joe and my wife said make sure that you buy the biggest one, because I don't want you saying in a year from now that you need to upgrade.
I have now sold my WSM and OTG and would love to part with my gasser but the wife said that is her grill!! (Love Her). She seems a ok now with it now that the sticker shock has subsided a bit. She also is happy that the other cookers are all gone. I really think that Kamado cooker is the best cookers for personal use. I am not knocking the big boys toys but what I am saying for the size, you can't beat the quality and multi purpose capabilities of a kamado.
I forgot to mention, the week that I was to pick it up, my wife received a Michael Kors watch and 2 new coach purses!! My dad once said there is always two ways to skin a cat!!!