I probably spent around £250 for components for my Prusa about 2.5 years ago. That's buying a kit of printed parts, stainless studding, nuts and bolts, and enough material to build several hot ends from scratch. I also bought the control board as a kit. I wouldn't build a Prusa again as there are much better designs around, but my guess is that my mk2 when I build it will cost around the same. I wouldn't use profile rail as the designs based on a gantry cut from sheet look much better to me but they need the ability to profile, say, alloy sheet.