Sort of... but it's only a problem if you can't afford it at some level (and not just money-wise... do you have the space, the time, or does it otherwise affect personal relationships).
Everybody has their own interests, and should be able to pursue them as long as they can afford it. It could be travel, cars, guns, houses, photography, woodworking, scrapbooking, or any number of other hobbies, and for us it's modeling.
If you are debt free (except for a mortgage), putting away enough for retirement, and feel comfortable spending the money, go ahead. On the other hand, if you're in debt up to your eyeballs or haven't put away anything for retirement yet, I'd strongly urge you to back off the hobby purchases and get your finances in order.
In my case, my monthly expenses usually add up to less than half of my monthly net pay, I'm debt free, and I'm saving/investing about 40% of my gross pay. The last couple months I have spent more than I usually do in the hobby, and I do feel some guilt about that. But looking at my larger picture, I can afford it. I lead a somewhat miserly existence, and probably ought to loosen the financial reins a bit anyway.