There are several factors in the pricing, @Damien71 that affect the final price you see when you make a reservation. First, if you start your seach without specific dates, you will see a price that usually reflects the lowest price, but when you enter dates the rate is reflective of the season and demand. Also, if the listing includes extra charges for additional guests, when you make a reservation, the final price will include all this plus any other fees and sometimes also taxes.
Still, if the rate you see still does not make sense taking all this into account, you should contact Air BNB to ensure it is not a system error. Here is a guide for contacting Air BNB. Good luck
https://community.withairbnb.com/t5/Help/Contact-Airbnb-A-Community-Help-Guide/m-p/16165#M728