I have never in my life built something and then wished I had bought it.
I've bought something many times only to find it did not sufficiently address my needs.
To be fair, I've also never built something in the time I originally estimated, often off by a factor of up to 10, but the end result is always better for me.
In my personal life I don’t usually wind up thinking “I wish I had bought this” but I do usually blow both my schedule and budget such that it would have been cheaper and faster to buy.
In particular I’ve learned that if I’m doing something new, it usually takes me three tries to make something I’m really satisfied with.
I've bought something many times only to find it did not sufficiently address my needs.
To be fair, I've also never built something in the time I originally estimated, often off by a factor of up to 10, but the end result is always better for me.