Of course it's an expensive process.
[opinion]
It's not, however, an expensive enough process to justify $20-$30 for a plastic bottle. Seems to me the manufacturing costs should be similar. I'd be interested to know why you say it's a more expensive process than glass - which requires a huge amount of heat (energy) and still requires molding, etc. As has been mentioned, there are some water jugs which are PET and cost a much more reasonable amount. It all boils down to my original comment: marketing. When I was entering homebrewing a year and a half ago, I was told that better bottles had a glass layer sandwiched between the plastic. I was told how much better they were. I've seen the better bottle crowd pipe up here constantly about how much a better bottle would be than (insert fermenter alternative here). Better bottle has done a kick-ass job of marketing - kudos to them! If I could sell a $7 product for $30 you bet your ass I would. When homebrewers latch on to something, it sells for a premium.
I've never used a better bottle, but wouldn't hesitate to use one if I was GIVEN one. That said, I'm confident that regardless of what I ferment in my glass carboys, regardless of how long I let them sit dirty and baking in the sun, I can get them clean quickly with hot water and oxyclean. I just have to be careful when handling them. Most of my carboys were made in the 70's and I'm confident they've got another couple decades in them - can the same be said for a better bottle? (hint - leave a glass carboy in the sun for a year and a plastic bottle in the sun for a year - which do you think you'd be willing to use after a year?)
Congrats to better bottle for awesome marketing - they've managed to sell a $8 product for $20-$30. Kinda makes me wonder, however, what the homebrew shops take is on the better bottles?[/opinion]