An question that always leads to so many different answers. best thing to do is to take the plans of the house and your specifications, bring it to 3 or more builders (check their references) and aks them to count on it. Remember when you compare not only to look on the price. Is IVA included? Look on the total costs such as Pool, lansdscaping, walled or fenced in property, Air cond, alarm, Solar panel etc, etc all this adds up, so the more specifications you have the better. My oppinon about the squaremeter price (only on the house living areas for a high quality) will be minimum €850/m2 + IVA (taxes), cave could be done for €250/m2 and Terraces €170/m2. Remember to check with the Camara what are planned around your plot the next years if there are any? Finally, I do not know if you are in place while the construction is going on, if not you have another problem, to find a person that you can trust your "life" with.
Good Luck