I learned how to sew as a young 'un, and I wasn't horrible at it. R. is considerably better at it than I am. I don't sew any more. He does. And quality of work product has _nothing_ to do with it. He does it, as near as I can tell, because it really chaps him to have to throw anything away that still has use left in it and I think he actually kind of enjoys the process. It doesn't bother me much to get rid of something (certainly not enough to remove and reverse a collar! Which I am still in awe of -- that's tough stuff!), and sewing machines lead to screaming. To be fair, I have done a little hand sewing over the years, when I really wanted something _that I couldn't buy anywhere_. Specifically, I wanted tab top drapes made from mudcloth. Where are you going to buy _that_?
Oh, and I did that by hand because, as I said, sewing machines lead to screaming.
I have a tough time imagining an economist looking at these choices and perceiving them as reasonable. But they really are, because they take into account the most important things in the lives of people with enough time and other resources to be able to do what they want, a lot of the time: do I enjoy doing this? more than something else? As opposed to, I just need to have the product and I'll slog through hell to get it because it's that or starve/freeze/lose the farm/etc.
I cook. R. cooks. At first glance, our cooking looks gendered: he tends to use the grill and cook meat; I tend to cook everything else and left to my own devices might not cook meat ever again (I mean, I _love_ me some poke, and sushi, and good deli meat...). At second glance, it looks like everyone-fend-for-yourself (poor T.! No, REALLY, poor T. It's amazing he doesn't starve). Occasionally, a relative (almost never friends) will be surprised by the kind of cooking I do/have done -- they would just buy some large chunk of the work done ahead of time, for example (I'm _still_ shaking my head over the idea that Barbara Kingsolver will _make her own cheese_, but never got around to making blender mayo). I usually explain myself by saying I'm doing it to get around allergies/sodium sensitivity/etc. But that's a load of horseshit. I've been cooking ridiculous things, working my way down the chain (I made pork dumplings, pot stickers. More than once, but one time, I didn't buy the damn wrappers. I bought semolina flour and made ravioli. I mean, _dumb_ amounts of work) long before I was a control freak about my health.
I just love it. Which, intellectually, sounds ridiculous, but this isn't an intellectual thing (altho I can make it one). I just love it. I don't feel at all compelled to do gourmet whatthefuck on any kind of regular basis; just doing ordinary day-to-day stuff is pretty rewarding.
There are other reasons to DIY (buffering one from the vagaries of the future, better understanding a product by going through the process, etc.). But fundamentally, economic arguments that fail to take into account the simple pleasures of _doing_ are never going to accurately account for Why DIY.