The test is simple: If you've ever bought a bike or bike part that you didn't need to continue cycling, or upgraded something when staying at that level would have worked just fine, then it's at least partially a hobby. Plenty of people get the AMA recommended amount of exercise on a $200 Xmart bike without problem. There's no reason anybody HAS to do it on a full carbon frame with Campy Record for 100 miles at a time.
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It's like riding a bicycle