Most likely the insurance covered a huge chunk of that.

It's a long story, but the TL;DR; of American healthcare is:

Healthcare providers over-inflate their costs and over-charge by orders of magnitude to insurance agencies. Why? It's because insurance agencies have whole teams and teams and teams and teams and teams (80% of insurance companies cost is administrative groups that just do this) of people that negotiate/argue that down to a reasonable amount. This means they pay a fraction of that initial bill, but they don't show that in the printout, instead they negotiate only "their part" of the bill, and send the rest they didn't negotiate down to the enrollee to cover up to their yearly maximum.

This is why you see bills for $100K+ and your amount owed is roughly $2-3K with insurance "paying" the rest.