I don't think it's especially a bargain, Yabby. Other similar places charge the same. In the past month I've seen it advertised as low as $21.50.I'm in Brisbane, though, not outback WA and perhaps it's a case of "fills ain't fills".

rehctub, I may not have made myself clear: I don't blame the servos for making a 50% profit (although i suspect it's nearer to 100

Anticeptic, many people confuse mark up with profit. I'm afraid it is impossible to make a 100% profit on anything.

If a car gas tank can be filled safely then there seems to be no reason why a bottle can't be retrofitted.

I think this is the answer to all problems except it may lead to job losses at the local hardware store.

I am in brisbane and I think I pay about $29.50 for a swap and go, althgough it goes on my fuel account so I don't bother to check.