I've been doing this for 8 years, have spent probably only about $1000 so far, and at this point I'm spending about $50/year - I need a new set of tires and brake pads every 2 years, and a chain/cassette replacement every 3. If starting over I'd only have to spend about $700 because I wouldn't have to buy all the cheap junk I bought in the past and thrown away.
I'm still on my first bike (a $300 Giant hybrid) and I have no real desire to buy another.
Any hobby costs what you decide to spend on it. You can get into most hobbies for a shoestring, or you can spend tens of thousands of dollars. It's really up to you. There are few hobbies that absolutely require a large investment, but it's easy to talk yourself into believing that you "need" to buy more stuff.
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Work: the 8 hours that separates bike rides.