But how much did the peanuts cost?
Last I checked they were on a par with a jar of shop bought PB. (Pound for pound)
Depends on the peanut butter you buy, I always bought the ones that are peanuts and peanut oil nothing else (often bought from market as supermarket doesn't always have) and using the TMX is certainly cheaper than that). Can make for a quarter of price of market bought. You can also do other nut butters or combinations which are very expensive to buy and get the consistency you want (we like quite chunky).

For me a big part of making my own is I am now not contributing to making of more plastic containers (glass isn't so bad but only pricy stuff comes in glass) I have one tub and I just refill it. (This is also true for other spreads, pasta sauce, curry pastes etc)