I called the first company I'd talked to, to confirm that, nope, their cost hadn't included unearthing it, either. I'm afraid the septic tank is going to turn out to be even more trouble to own than it is to buy. Hmp.
Anyway, I asked Juanita if we could do the house and septic tank inspections on different days, so that I needn't pay the small fortune to deal with the tank if the house has termites or is sliding off the foundation or some other deal-breaker. So I feel a little better about that.
Wish I'd suggested that last Friday; then I could've had the house done on Monday after all. Sigh. One more day to wait.