This is certainly an interesting question to think about. I few years ago, I never would have thought I would spend some of the money I have spent acquiring certain games in my collection, or indeed the amount I have spent bulk purchasing cheaper games in volume. Heck, 6 months ago if you had told me that I would spend over 500 bucks buying Sculptors' Cut and Stunt Racer 64 I would have said no way. But, as time goes by, and as you get used to opening your wallet to buy the things you desire, it gets easier and easier to do so. Right now I look at what I've got, and I feel a sense of pride and contentment that I had the guts to actually make some of the deals I've made. Collecting from abroad is not easy, you get way more doors slammed in your face, and you have practically zero opportunity to simply stumble across some of these items like you might do elsewhere. It takes a lot more planning and active thought to collect, when you want the things I want and when you live where I do. To have taken my collection to the modest stage that I have, with so little waste and so many key items I desire, it may sound sad but it does feel like an accomplishment to me, at least in terms of fulfilling my potential within my hobby.
So, who knows... In a way I could see myself purchasing any item for full market value, if I had the money and I wanted it bad enough. My interests certainly don't lie in the sealed, high-end collectible market, so that rules that out. And I collect relatively slowly compared to other big spenders, so usually I'm happy to work on a limited number of goals for a few years at a time. But, lets face it, any game you can afford to purchase at FMV, you could resell for close to that again, or perhaps even more if you wait a few years. If you are comfortable with money, and don't fear loosing your livelihood and being in dire need of immediate cash, there is very little risk in buying games at FMV, imo.