I wouldn't be so quick to judge a book by its cover or the cost of a coop by its appearance. Many recycle and reuse and that doesn't necessarily mean that the end product won't look far more expensive than it really was.
Every window in my coop was free, recycled from a friend who does home renovations. We saved them for a year before we had enough. The more free windows we used = the less lumber we had to buy. The tin roof = free, too. A roofer friend gave it to us, it has a few cosmetic dings so he couldn't use it for a home. The siding boards were from Craigslist, a steal from a local man who has a sawmill and too much inventory. They were odd sizes but we made it work. A good bit of our initial 4 x 4's and 2 x 4's were left over from decking projects that we had done. Yes, we did have to buy some stuff, batten boards, extra 2 x 4's and 4 x 4's, and hardware. The hardware was the most expensive but that's where we chose to spend our money as we didn't want to compromise on security. The end result is we have a coop that looks far more expensive than it really was.
A hobby? Yes and no. I have them primarily for our personal use of their eggs. I feel that their eggs are better for us as I know how the birds were treated and what they're eating. I personally enjoy interacting with the chickens so I guess in some ways it could be considered a hobby in the same fashion that having a dog or cat or parrot would be considered a hobby.
Cost effective? I doubt it. In my case, I can't free range due to poultry regulations in my area so I must provide them with more feed than those who can free-range. Regulations also prohibit me from selling eggs and from processing birds for meat on my property. I really enjoy gifting eggs to friends and neighbors and I also use them for barter. However, for me to eat them as meat birds I'd have to haul them to another county and pay to have them processed. So, no, not cost effective for me to do that.
Does it matter? Absolutely not. We're doing something that we enjoy and are providing our family with both the experience and knowledge of raising chickens and having fresh eggs. In our case, that experience and knowledge is now being passed down to the third generation. That's all a big plus and is worth its weight in gold. If you factored that into cost effectiveness, we'd then be way ahead.
Some things in life can't be measured in dollars and cents only. For some of us, raising chickens is one of those things and that's positively okay.