Culling took place in the county, for a third year, from 31 August to 12 October, with 279 animals killed.
The costs for the badger cull will be met by the Department for Environment, Food and Rural Affairs (Defra).
Government ministers and the National Farmers' Union believe culling badgers will curb TB in cattle.
Opponents say shooting the animals is not a good way to control the disease.
Stop the Cull said fewer people protested in Somerset than in previous years because efforts were focused on Dorset which was included for the first time.
Spokesman Jay Tiernan said: "Quite a low number of people turned out, so if that still costs half a million pounds to police then what is the actual cost of the cull?
"It's a matter of fact people across the board are against the badger cull.
"The protesters are always going to be there and the taxpayer is always going to lose money."
Gloucestershire Police revealed last month that policing the badger cull in that county cost Â£425,598 in 2015.
Policing the badger cull in Somerset in 2015 cost Â£555,514, new figures released by the Avon and Somerset force reveal.