Can a hotel change a room rate reservation quote after the room has been paid for in advance?

If the hotel made an unconditional offer (i.e. the offer didn't say something like "subject to change anytime before occupancy"), it is bound by it unless it was obviously a mistake.  So, if the hotel accidentally screwed up a decimal point, and made the room rate $2.50, instead of $250, it would be an obvious mistake and it would not be bound.  Otherwise, you have a contract to occupy the room at the offered rate.  As a practical matter, however, the hotel is probably not going to allow you to occupy the room at that rate and you are going to have to sue it, which is a hassle.  Also, if you do compel the hotel to honor their rate, it may retaliate by giving you a bad room, and/or poor service.  You may be better off getting a refund and finding somewhere else to stay.