I must say, I've enjoyed this thread immensely. A lot of good points have been brought up, although I'm also a bit saddened by a few of the things that have been said, as well.
First, in direct response to the question as it was posed by the OP. Is being a SAHP a "waste" of a degree that one previously obtained? While it depends a bit on the exact situation, I'd generally tend to think that no, it's not a waste. That said, it's important to ask why did one get the degree in the first place? If it's for overall life experience, because you enjoy education, or just wanting to have specific skills that may be useful in life (job, or otherwise), I'd say any of those is a great reason to have been to college, and isn't a waste at all. The opposite case of one who had to finance the entire bill by loans and knew/suspected with little expectation to earn income as a result (which is not the OP at all, of course), then I'd say it was a rather poor decision.
What surprises me a bit, is how much discussion has been generated about equating degree = getting a good job. As I've alluded to in some of my specific responses, I think the nation has generally taken this mentality too much to heart, and in part created a double-edged sword... the perceived importance of the degree (and yes, in some cases that perception may be reality) has also led to a degree being less of a distinguishing factor among job candidates.
It's been "shown" that people who get more education make more money, right? Well, sort of. What's been shown (yes, many times) is that the average income (usually "median" is taken as average) among those employed tends to follow an increasing pattern. Namely, those with a doctorate, on average, make more money than those with a masters, and they make more than those with a bachelor's, etc, etc. This demonstrates pretty convincingly that there is a correlation between amount of education and income.
What this does NOT show however, is that there is any type of causal relationship between the two. Many bloggers, journalists, and commercials for two-bit fly-by-night "universities" (my favorite of all) are quick to quote the statistics in a way that assumes such causation. The whole correlation vs causation misunderstanding makes the income level statements a very tired argument to my ears.
What I'd love to see (and doubt I ever will) is a study that successfully isolates the education variable from others. In a pure sense, this is of course impossible, since you can't compare the same person against themselves with and without a degree (over the same time period of their life). Let me propose a thought experiment like this... let's take a sampling of a whole bunch of people who were in National honor society, or graduated in the top n% of their class, or have an IQ above X. (What group of people you pick is not important, you get the idea) Now let's compare those who did go to college with those who didn't go to college... and that's where we have a problem, the overwhelming majority do in fact go on to get more education, so those that don't are already rare outlying cases. To put it yet another way, when you compare those who complete more education against those who don't, you're implicitly making a distinction between those who are hard working, motivated, or possibly gifted in various ways, against those who aren't... and though not identical, these are largely the same traits that ultimately do well in the work-force... so it should come as no surprise whatsoever that, on average, those who go to college make more money. But... it doesn't mean that if person X goes to college, he/she is magically going to make more money.
Okay, all of my rambling aside (my apologies), one thing I'd really like to thank everyone for, is pointing out something very important that I had hither to never really considered. The value of education for either life experience or because one simply enjoys learning. I think these are probably--at least in my mind-- the best reasons for getting a degree. And to the OP specifically, your degree wasn't a waste at all. For anyone else, if getting a degree is something you want to do (for personal satisfaction, or because you've made a well thought decision that it's a good idea for your career or whatever else), then I would say definitely go for it, and don't ever regret it
