As Smidge said earlier:-
The real value of something is what the buyer will pay and the seller will sell at.
I don't doubt that there is land out there for 1500 euros an acre and possibly cheaper, but it depends if it is the land you want. If it is then great, if not you have to pay what is asked for the land that you do want.
There are many people out there giving different estimates. Back in the boom many were saying 6000 a jornale for land with water and 4000 for land without. I know for a fact many people paid this , or close, at the time for what they wanted, as it was what they wanted and were prepared to pay it.
It also seems like everyone should be coming to you Bruixot for their second hand needs if you can beat all the prices on here by 50%  ;)