I think cycling other than at a high competitive level will always be considered a hobby by someone who is not a cyclist themselves. No matter how much you spend, how much time you spend, how dedicated, or much you love it, it will still be just a hobby to them. This isn't meant to cheapen or insult you as a cyclist. This is just fact. Same as you would call a lawyer who collects stamps a hobbyist even though they've been doing it for 25 years and have spent over $10,000 on a single stamp before. That person's profession is law, not stamp collecting.
I think the book definition is crossed when your hobby ceases to become something you do on your own for fun and begins being something you do to earn money. That said, it still still possible to maintain cycling as a hobby while you work as a bike mechanic or work in the cycling industry. I'd guess there are hundreds of people that work for Canon as non-photographers that would call photography their hobby. Same with auto mechanics that race cars as a hobby, etc.