Toilet not filling, plumbing query

Extremely random, but recently my toilet stopped filling up. So I called out my plumber and he changed the valve. On the invoice, it came to a total of £90, he also carried out other work, but the toilet took him 5 minutes.

Can somebody tell me whether this is expensive? As from what I can see, the only thing that’s been changed is the valve, a new system hasn’t been installed.

Any infomation is appreciated!