Last week I was using the techniques and strategies outlined in this comprehensive series to book a four night hotel stay in Hong Kong. I started my bidding at $85/night and slowly raised it in $5 increments all the way up to $140. Even at the $140 price point, Priceline was not accepting my bid, and was not even suggesting I should increase it by some specific amount in order to be accepted. On the other hand, it also did not tell me there were no rooms available, but rather simply kept encouraging me to rebid and rebid at ever higher rates.
I did not fall into the bidding frenzy trap, and instead turned to Expedia and booked a nice room in a nice hotel (Butterfly on Wellington) for $134/night. Because Expedia do not charge any booking fees, and Priceline does, the actual saving to me was considerably more than what ever it might have seemed to be if I were to continue bidding ever upwards on Priceline until a bid was accepted.
My point in recounting this to you is to point out that one should never assume that a careful and optimized bidding process through Priceline will always result in getting a hotel room for less than the going market rate. Because only some of the hotels in any given area work with Priceline, it is entirely possible that Priceline might have no remaining discounted rooms on offer, while a broader hotel booking service might know of good value rooms at hotels that do not participate in the Priceline program.
In general, Priceline is most likely to offer the biggest savings in North America, particularly at times when the hotel industry is weak. When the hotel industry cycles to periods of fuller occupancies, Priceline's ability to get massively discounted 'remainder rooms' reduces.
I have edited several parts of my series on How to Save Money when Booking Hotels through Priceline to reflect this reality, because I do not think I previously gave enough prominence to this particular potential downside to using Priceline.
This is not to say that you should not now use Priceline, it just means, as always, you need to be well informed prior to bidding.