it's not cheap but it's very nice if you like your gin! Yes, you could pay £5 in the local off-licence for a non-branded gin. The deal here isn't about how cheap you can buy gin, it's about how cheap you can get this specific product.
Camelcamelcamel says the best price it has been on amazon is £30.56 so this is very close. Looking around it seems that about £35-38 posted is the going price for this.
If anyone has any gin recommendations then feel free to add them in the comments. Brockmans gin is also good as is Silent Pool (also has a lovely bottle)