I'll assume that downvotes mean I wasn't clear: the US is currently spending that much ($150B apparently, I haven't checked) on R&D for drugs. It's just doing it through different means, presumably by paying higher insurance premiums and healthcare costs that end up going to drug companies to fund their R&D. If instead we payed that cost through taxes, then there's no theoretical reason why it would have to cost any more. So why would it be too expensive, given that we already pay that much via a different route? Of course, it's not politically expedient and won't happen anytime soon.