Well, I can tell you the most money that I regret spending. And that was ~$300 for Round4. I sent ~$300 to 7bit in December 2011, and I still haven't received doodley squat.
We're going on 18 months now, and still no keycaps. I don't even remember what I ordered, so I can't even tell you what I paid for. But besides Round4, I don't regret any of the other money that I've spent on keyboards or keycaps.
Round4 however, is a royal sh!t stain.