Perhaps I should have known by the way the name dripped so easily from my daughter’s tongue.

The TI-84, she said. That’s what I need for algebra.

Hmm said I, observer of years of math torment and purchaser of the Algebra for Dummies workbook that has haunted part of the child’s summer. She wants a 4.0 to get into a good college, though, and I offered that perhaps if she earned an A in algebra for first quarter, the magical calculator would materialize. We virtually never offer bribes, but light in her eyes for math made it worthwhile.

Bwahaha. Of course both children came home from school Tuesday with supply lists, and of course both specified the prized TI-84 – Plus, no less. I consulted the Staples flier, which told me I was facing about $80. (“What’s a rebate?” the daughter asked. “A coupon companies hope you forget about,” I told her.)

Then we arrived at the store and saw the end cap of calculators. Alarms should have gone off at the mere existence of a calculator end cap. The $80 one was snatched up but wait! There were multiple editions. Ah, but the $90 silver edition is for geometry, which my sophomore son is enrolled in.

The children started to turn toward the cash registers, each with a calculator in hand. Nuh-uh, I stepped in, having heard my son say earlier he could have used a graphing calculator, oh, about five times during freshman algebra. One, I said. Share, I said.

Muttering. Too bad. The last warning from Mom? “Lose it and you replace it.”

It’s an investment, I told my husband. If they hadn’t hit us this year, it would have been next year with trigonometry, so we’re biting now. And once again, the start of school is one of the most expensive times of year.