In this paper it will be evaluated and analysed the costs that compose a Solar PV project: modules, inverters and BOS (including the procedure and administrative management, taxes, sales effort, etc.) with the purpose to justify its big reduction and detect the responsible factors for such evolution: economy of scale, technology improvements, etc. Gathering most recent data for the registered prices, analysis of its evolution and future estimations by using the Learning-by-doing method. Also, it is compared such costs among the different countries, and it is also analysed its difference. Moreover, it is also studied the final price of the energy by means of the LCOE and the auction prices