I mean, if we’re going down to tools, a cheap 500W hammer drill comes in at £18.23 new (https://www.amazon.co.uk/Silverline-265897-Hammer-Drill-500/dp/B002QRYFGA/ref=sr_1_2?ie=UTF8&qid=1495576329&sr=8-2&keywords=Electric+drill); by my calculations, that comes in at $35.25/hp