Well, seeing as I'm 33 and know how much I earn, then I know it to be possible, BUT, the vast majority of people in all professions won't be earning anywhere close to that until they have a significantly larger amount of experience.
I'm lucky, I've managed to get well qualified and experienced in a short space of time and I'm in a narrow field where there are few people of any age with the experience I have. So, I'm worth more to my employers and I have the ability to dictate to them my salary demands, rather than the other way around.
I know full well what most people get paid and £100K is a very, very unusual salary for someone under the age of 30 unless they are working in the city.
IF the supposed pilot shortage ever appears, then things will be better for pilots when it comes to pay.
Though there is a shortage of experienced people, which is why places like RYR are throwing people into the LHS so quickly.
I have one friend of mine who is doing his command course at the moment. He's been flying for RYR for less than 4 years. He's very good and will do fine (I hope) but with less than 4000hrs TT he's going to be in charge of a 189 seat passenger jet...
One last thing. When I said 7 or 8 years, I was probably being generous, that's the absolute maximum, most people I know didn't manage to find jobs in their chosen careers until they were closer to 25 and so it's perfectly feasible for a uni graduate to be 29 and only have 3 or 4 years of working experience behind them.