In 2001, I applied to five colleges, which was a bit short of the six to eight college counselors suggested. But I also early actioned and was accepted at my top choice, and the deadlines for safety schools was after that acceptance, so I might have wound up at six-to-eight otherwise.
Back then, the Common Application was less common than it is now, so the marginal cost of applying to yet another school was substantially higher than it is now. You had to fill out another long-form application, for the most part. Now, once you have six applications buttoned up (dream school, two nice but not dream schools, two better safeties, and a straight-up bottom-dollar safety, say) applying to the next school is a matter of checking another checkbox, and creatively adapting one of the essays you’ve already written to suit the next school. Not a high marginal cost.
So I suppose 20 schools isn’t insane. But it does seem like too much.