Oh, well then I guess we'll have to continue underpaying employees.

And employees will continue their migration outwards to other firms. They'll tell their (now ex) coworkers about how much better they're paid elsewhere, and those coworkers will start to sniff around as well. It's a lose-lose situation. If employee retention is the goal, better to strive to pay top-of-market (see: Netflix, most small/medium consulting firms) than let your best and brightest be woo'd elsewhere.