[Non-Tech] Descaling for 1/3 of the price
Totally non-techy post ahead:
Most supermarket/shop descaling powders (the little sachets) work out at about £15/kg, given that all they contain (for the vast majority of them!) is citric acid, it works out a lot cheaper to just buy Citric Acid in bulk (Amazon link: 1kg Citric Acid for £5) and use exactly the same quantity.
My skillset has matured somewhat since then, which you'll probably see from the posts here. You can read a bit more about me on the about page of the site, or check out some of the other posts on my areas of interest.