Informed by who? Hospital performs services, sends out a "bill" 30 days later, patient responds "due to the lack of published pricing as per federal reguation, no contract was formed and thus this bill is invalid". Are you saying the hospital would then react by stopping providing care to all patients from then on? Why wouldn't they react by you know, complying with the law to stay in business?

A contract has to have defined consideration, otherwise it is not a contract. Time and materials (hourly rate + cost/plus) is another standard form of financial consideration, but "we'll charge you whatever we feel like at some later time" is not.