I think you fail to understand the basics here Bill, the people who have mega lenses are either professional and the lens pays for it's self or they have a lot of spare cash.
Neil, I don't have a lot of spare cash...though I don't drink or smoke so perhaps I do have a little bit more than some
You raised an important point in an earlier post, if someone is happy with the images they are taking then that is all that matters. However when people say "You must be crazy lugging around a large lens like that", don't be surprised if I say "You must be crazy if you think I like that photo you just showed me."
Don't get me wrong, there are people who take amazingly rubbish photos with expensive kit (all the gear no idea, kinda like me), and others who take amazingly good photos with very modest equipment. However the thing that I always find is that the images that are (in my eyes) excellent are almost always done with semi to pro kit. If this wasn't the case all the pro togs would be putting their cameras away in their shirt pockets. Now to some degree it depends on what you like to shoot, at the long end there just isn't any contest.
Superzooms do have their place, they are light and convenient and you will probably have one with you rather than the heavy camera+lens back in your cupboard at home. However these days I try to only take photos that I want to keep, not 1000's of shots that will never get a look at ever again. I
want to take my heavy camera and lens with me because I know it will deliver the results I want. I bumped into a pro wildlife photographer a number of years ago and the one thing that stuck in my mind that he said was "Rather take one great photo on an outing than 100's of mediocre ones".
I have had "superzooms" in the past, I also had a Panasonic G1 when they came out and I was happy with the images they took at the time, however I wanted more, but like already said, if you are happy with your images, that is all that counts.
I'll agree that £10K is a bit too steep (effing vertical), however 1/3 of that can get you some lovely glass that you will have long after your Canon SX50 has biodegraded.