Well, metal shavings can and do happen more often than you think. Maybe with the manufacturing processes these days, its more rare, but other contaminants are present in the oil, such as protective chemicals/coatings that keep the engine conditioned before fluids (oil, etc.) are filled. Being a tool and die maker in the automotive industry, I know a few things. Mind you the parts are deburred and hardened before installation, there is STILL metal-to-metal (mechanical) contact between parts that cause them to wear down, especially during the initial break-in period when everything in settling in (hence the term "break-in").
Honeslty, if you really think about it, the engineers at BRP don't just randomly pick a number or a period in which you should do your initial maintenance. It is designed that way for a reason! If they REALLY wanted money from you, they would make it every 10 hours, but they don't... Its only once you do that and every so often after that.
Imagine never changing the oil in your car because you thought some guy at GM wanted to take your money? HAHA! Good luck with that engine. And I think that if you can't afford to do the first 10-hour service or any of the following services, then maybe you should either get a used machine that has had it done already or don't bother getting one. Like I said, it just annoys me a bit when people don't take care of their toys and then complain that it breaks.
Just my two cents. And for those of you who opt to do it yourselves, that's great! I honestly respect that and great on you that you're saving some money in the process. Personally, I don't know much about my Sea-Doo and I haven't the time for it. But despite that, I will still take good care of mine (maintenance, etc.) so that it'll last me for years to come!