Hotels have 2 main prices.

The RACK rate.  This is the highest price a Hotel can sell.  It is very rarely sold and you might see it is during very busy times such as maybe the Ryder Cup or the recent U2 concerts in Dublin.  

The main rate a Hotel will sell is the Best Available Rate.  This is the best price a Hotel can get for a stay for a particular night.

Some 3rd party websites claim you are getting up to 75% off the regular price of a hotel.  Not so.

What they do is base this discount off the hotel rack rate.  lets say the RACK rate is €400.  The hotels best available rate is €100.  Some sites will claim you are now getting 75% off.  Do you really think you are getting 75% off?

If you are booking a Hotel and the website is saying the normal price is €400 but we will give it to you for €100 it is best to use your common sense.