On average real costs run about 20% of charges, so $90k should translate to about $18k.
While average reimbursement will be about 102-104% of cost, it varies a lot by payer type. Commercial insurance would typically pay a little over 2X cost, so in this case 35-40k. Remember the hospital is offsetting 10-20% of the population who don't pay anything (uninsured, no assets, walk in through the ER), and folks on government plans where the price is set between 60-80% of cost.
Yes, a little over half of what you and your employer pay in premium for your care is really just a federal tax under a different name.