The biggest hobby I have other than wargaming would be hunting. This may not seem like a hobby to some, but it is something I do in my spare time that I don't need to do, thus the hobby classification. Every year I can't wait for September to come so I can get into the woods with bow and arrow in hand, hoping for a deer to come into under 25 yds(sometimes as close as a few feet). The excitement is awesome. I also hunt deer with muzzleloaders and rifles. I also do some small game hunting, including doves and rabbits. The outdoors is a great place to be and I highly suggest it. Some of the things I have purchased over the years to help with my hunting endeavors are:
NC Hunting/Fishing License -$40
Remington .270 WSM with Scope - $800
20 Bullets for .270 WSM - $45
Clothing/Boots/hats/gloves/socks/etc for Warm, mild, cool, cold, very cold weather -at least $1000-$2000
Cover Scents/Calls/Accessories - at least $250
2 Scout Cameras - $250
2 Ladder Stands - $250
3 Lock-On Stands with Ladder Sticks - $250
Ground Blind - $150
Muzzleloader plus Scope and Accessories - $600
Compound Bow with Accessories - $800(arrows cost $10 each plus broadheads are $12 each, so $22 per shot, usually good for 1-2 shots through game)
Four other guns of various caliber - $2000
Skinning Knife - $125
Processing Equipment(vacuum sealer, bags, grinder)- $500
Keep in mind most of the above equipment is in the lower to middle end of cost scale for comparable items. I usually look for products that will get the job done and are still affordable. I don't have the extra income to afford the highest quality items around. Shopping around is a must as hunting equipment ranges wildly in costs and qualities. As in wargaming, you can buy cheap knock-offs or top-of-the-line products. At least with GW stuff you know you are getting the best of the best and the cost aren't that much more than knock-offs.
Like wargaming I have been collecting the things I want/need for hunting in same manner. Spending a little over $1,000 a year has kept it enjoyable and affordable for me. And like in wargaming, after a few years I can spend little on new things and just buy the essentials to keep this hobby really cheap, while providing hours of enjoyment(and no you don't have to harvest an animal to have fun, I just like being out there spending time in the outdoors). It has taken years to add the above to my collection. I still add new stands, accessories, clothing to this as I see the need arise. When it gets near hunting season, my models hit backburner until afterwards. I spend lots of time scouting for new locations, putting in stands, and practicing my shooting. It keeps me in shape as a side benefit also. I get plenty of hiking in and just spending time in the outdoors is good for the soul. Just so I can sit in a tree in sub-freezing temps hoping a nice one will walk in range. The cost for me is comparable to wargaming, but at least in 40k it doesn't cost me $2.50 per bullet or $22 per arrow.
Again, this is another hobby that has a similar costs to wargaming. It has a larger startup cost, while becoming much cheaper after initial investments are made. Also, it gets me outside more in the spring and summer. My 3 year old and I have a lot of fun out there planting seeds and plants, watering and finally picking the fruits of our labor. Though we have only picked a few squash, cucumbers, onions and potatoes so far. There are a lot more things to harvest coming up later in the summer.
My last hobby would be fishing. I don't go as much as I would like with the small children and water. This is very cheap for me actually on a per year basis. Over the years I have collected enough rods and lures to have a fun time fishing in local streams, rivers and small ponds. In my case, fishing is relatively cheap. I only go a few times per year and spend very little money doing so. The startup costs for the fishing I do is about the same as a good 2,000 pt army, again this can be spent over a period of time. Granted I don't do any saltwater fishing, or going to large lakes where you need a fishing boat, truck and lots of gas money. I keep this small and it is fun for me.
I used to snowboard a lot when I was younger. This is another hobby similar to wargaming. The cost of the equipment you need will be about the same as starting up the wargaming hobby. But you then have to add in the constant lift ticket purchases needed to go, costing $20-$40 per day usually, not to mention I have to drive almost 2 hrs to get to a suitable ski resort.
A hobby that I would like to have is auto racing, not Nascar, I like more grassroots style autocrossing/road racing. However, this is too expensive for me to get into, so I just watch on TV. No, I don't go into racing forums and put up hate posts about how it is too expensive for me. I just don't get involved in it. Just because you can't afford to participate in a hobby doesn't mean you should hate the companies involved in it.
Well, there are a few examples of things that are considered hobbies and their costs, that I am actively involved in. Like any hobby, you can get into any of these as little or as deep as you want. Which means spending as little, or as much as you want. Wargaming can be enjoyed for years on as little as $1,000 total, as can hunting, but in the end the sky is the limit on how much you think you have to spend to enjoy yourself.
I feel like all the hobbies I enjoy are worth every penny I spend. If I didn't I wouldn't have that as a hobby. I know models are expensive, but it's a hobby, enjoy it or stop playing. So far though, I think the cost is affordable for the amount of time enjoyed and it really is a lower-cost hobby really, at least over a period of time. I do think the general consensus is that the startup cost is formidable for some. I know I couldn't go to the FLGS and throw down $600+ on some models in one day. The wife would probably kill me, just kidding, well maybe I would get lucky and only be maimed severely. If I spread this out over a several months or a year(and don't let her find out), the cost is a little easier to swallow. Personally, I think it is one of the most affordable hobbies around for what you get. If you can name some hobbies that are cheaper, let me know what they are, I am having trouble coming up with more than a couple. On the other hand, I could name over a dozen in seconds that cost more, some lots more.