I’m here to pat myself on the back, as I resisted the $30 Amazon come-on which expired yesterday. I was mightily tempted and (of course) I had books I could have applied it to, but between the amount of the outlay and the fact that it’s not really as good a deal as the gloss put on it by Amazon*, I was ultimately able to let it run out without acting.
*Although I’ll note that Amazon no longer makes the claim about the size of the savings in percentage terms; I infer from that they were called on a deceptive practice. So in fairness to Amazon, they only refer to the dollar savings now. The (real) percentage terms are still useful in comparing deals, however.