I have recently completed this absolute beast which takes pride of place in my collection. I greatly enjoyed the build process and the instructions were incredibly good quality. All in all I think I spent around €250 on parts although that is very ballparky as I gathered the parts over some time, while also getting parts for some other projects. I'm not certain but I believe I only had to buy around 80% of the parts as I was able to gather many parts from my existing collection.
Many thanks to @RenegadeClone for his masterpiece along with the excellent instructions at such a low price!