We made butter for the first time this weekend. We succeeded, but when factoring the cost of double cream, electricity and the messy blender, it makes more sense to buy a cube of Lurpak or similar.
Butter is worth making at home because it's quick, easy and cheap.
A 250g block of supermarket's own brand butter is about £1.60, or £6.40/kg.
A 600ml tub of double cream costs £2 and that will give me a yield of 400g of butter in five minutes.
The electricity cost for a 300 watt hand mixer for five minutes is tiny, probably about tuppence max.
So at this stage I can have 400g of butter for around £2, that's just £5/kg so already cheaper than shop bought. Add to that I also now have 200ml of buttermilk, which would cost me 80p in the supermarket, and it's even more worth it.
BUT, I wait until the cream is on the short-dated shelf where I can buy it on the best before date for 10p for 600ml. It's actually better to use cream that's at that date or just beyond, it churns into butter faster. (It also speeds up the process if you take it out of the fridge and let it get to room tempereature before churning.)
So now I'm getting 400g of butter for 10p or 25p/kg, plus that lovely buttermilk that I can use in making my bread. That's an absolute bargain!