Haha!! OP here, thinking the exact same thing!
Just to bring things back around, my original question was about whether it's really that much cheaper to DIY compared to buying a pre-built system. There have been many helpful replies that actually addressed that question.
My takeaway is that, yes, it's possible to save a few bills by shopping around, buying used, building panels, etc. But the savings is not tremendous. It seems that the true advantage of building a system from scratch is the enjoyment of the process, knowing your system inside-out, and having full control over all design decisions. These are all totally valid reasons.
However, I think that ultimately, for me, I just want to make delicious beer. With my work and family schedule, finding time to build a panel and source all those parts would take months. Not to mention building a ventilation system, running 240 GFCI (which I would NOT do myself!), etc. So I think I've come down on the side of "Buy."
Over the last few days, I've read the entire 69-page Grainfather thread, and it sounds pretty great. Yes, I would lose the ability to do 10g batches. Yes, it takes longer to heat to temp. BUT, I would be able to brew in my basement, kitchen, back yard, friend's house, etc. And I appreciate the slick, all-in-one design. I have seen TexasWine mention the Brau Supply system in several threads, and it looks like a possibility as well, although I'll admit the design aesthetic of the Grainfather might be worth the $200 difference to me. We'll see...
Thanks again for everyone's (mostly helpful) posts.