What you need to get your head around, is the idea that Penhaligons are a huge step up from standard high street fragrance brands like Hugo Boss, Armani, Davidoff etc. Their fragrances are more complex, more layered and generally more classical, therefore not changing from season to season.
When you consider that a bottle of gucci can cost upwards of £40, it suddenly doesnt seem completely unreasonable to ask £60-70 for something considerably more complex, produced in much smaller quantity, in much nicer bottles, by a maker with a dedicated high street presence.
Ive used a few of their smells, and i'm a huge fan of opus. The first time my girfriend got a whiff of opus, she was taken by its complexity and tones immediately. Now she steals a little spray of it now and then when she thinks i'm not looking.
BEsides... if you phone the factory outlet stores, you can get 2x 100ml for £60... thats £30 a bottle, so they end up cheaper than the competition, and better.