When does a hobby become an obsession?

I've been thinking recently about how obsessed people often become by their particular hobbies, and the amount of money they can sink into them. I've decided that no matter what you do for recreation, you can find someone else who is way better at it, who spends way more time at it, and who has put way more money into it.

Here are a few examples:

• Ann and I enjoy scuba-diving. With the presence of two kids it's not something we get to do much anymore, but we still enjoy talking about it and looking forward to getting back into it. But whenever we've been, we always run into "those" people, the ones with the multi-thousand dollar underwater cameras, wearing several thousand dollars worth of gear, and they're on their seventh scuba-diving trip. That year. And it's only April.
• One of my long-time hobbies is computer gaming. Keeping decent hardware takes a non-trivial amount of money, and games easily run between 40 and 60 dollars. A standard computer game can take up to 20 hours to complete (although I have one that I've spent, embarassingly, over 100 hours on (curse you, Oblivion!)). But I heard a podcast a while back about a guy who'd spent about 2,500 hours on an online game called Guild Wars. And the game had only been out for a year and a half or so. They figured out that this guy had to have spent around 5 hours every day for a year and a half to log that many hours.
• This afternoon the Monkey and I went to Fry's. In the parking lot, they had guys showing off their pimped out cars. You know the ones I'm talking about, with the custom rims and paint jobs and a sound system that sounds like he's performing nuclear warhead tests in the trunk (and the driver always has a Bluetooth headset). There was one guy who had an Excursion (base price, probably around $40,000) with a blue and orange paint job (I'm guessing several thousand dollars), an XBox mounted into the dashboard, a video screen in the dashboard, another small screen over the backseat, and then two ENORMOUS videos screens over the back seats (probably 15-inches each). So that's FOUR SCREENS in the car, twice as many as I have in my house. Then he had the sound system in the trunk, with a huge sub-woofer. I'm guessing the entertainment system alone was several tens of thousands of dollars. And of course the entire car was detailed and spotless. But it gets better: right next to the Excursion was his motorcycle with an identical paint job, and right next to that was the helmet for his motorcycle, with an identical paint job. So the whole setup had to have been well over 100 grand.

So how is it that somebody goes from saying, "I enjoy swimming underwater," to "I'll spend every spare dollar and hour I have to have the best gear, so that I can swim underwater"? How does someone go from, "I'll enjoy a couple hours of video-gaming every now and then," to "I will forget about having a life in the real world, so that I can have a life in this simulated world"? And how on EARTH does someone say, "You know, I don't think my kids really NEED to go to college; what they need is to be able to play their XBox on 15-inch screens in the back of the car, while I ride my matching motorcycle next to them!"?

Maybe I'm just getting old and crotchety...