I'm not going to go through what other people have already done, but compare what we do with that of another professional of similar level of responsibility:
Surgeons: How much do they earn? They have a job of "fixing" people and saving lives and under a considerable amount of pressure. I wouldn't say stress as such as you can't get to the level of surgeon or consultant without considerable experience and more to the point talent. Talent is what I believe we posess; to fly in the first place, as not all people have the capacity and ability, together with the mentality to react appropriately under pressure (sometimnes extreme) and all this without the passengers even knowing anything is wrong.
Do they take bi-annual tests that determines if they have a job the next day?
Do they pay from £40k to £90k for the training
I'm not saying I'm a brain surgeon but I do believe that we do have a similar level of responsibility and profesionalism.
On the complete opposite side of the coin, do you really think that the City traders gaining millions in bonuses every year earn their salary? I think the recent credit crunsh answers that question.
We get paid what we should in my opinion. I get just below £40k basic and can make another £20k a year on allowances. I'm very happy as a first year F/O to be paid this much. (oh and I didn't pay for my place in the airline and didnt pay for the TR, just incase anyone decides to throw that one back at me).