Of the woodworking I do, I find toy-making the most fun. It’s a chance to be creative, work to lighter tolerances using [much] simpler joinery, make a kid happy, and use up scrap wood.
Here’s a picture of a train set I just finished. It’s made entirely of scrap wood, save a $1 dowel, using hand tools(*). The darker wood is douglas fir and the lighter wood is cheap warped SPH (spruce-pine-hemlock) framing that I planed straight. The dowels (chimneys, axles) are oak.
(*) My only powertool is a small proxxon drill press I use to drill pilot holes for my chuck and brace.
Initially, the trickiest part was cutting out all the wheels using a fret saw but it soon became easier as I learned how to use it better. BTW I use it backwards sawing on the pushstroke, but whatever. The hardest part was sawing the angles on the cow catcher (yes, city-peeps, it’s really called that). The boiler was made out of a 2×6, doubled up with glue and formed with a block plane. The only thing in making these that would be hard for a novice would be the exact cutting of the front of the engine room. This was cut and undercut much like a dovetail. Otherwise, if you think about it, a train is just a simple kind of box with some extra wood parts glued onto it.
I have no idea how long it took me to make it. I made each part using 5 minutes here and 5 minutes there. My total cost was $1 for the dowel. The rest of the wood would otherwise have been campfire fuel.
Cost if you had to buy it? Hard to say. A quick google search didn’t reveal anything for sale at the same level of complexity (you ain’t seen nothing yet). A simpler model of comparable size but without push rods costs $50 retail. Maybe this one would sell for $75 in some fancy artsy corner store?
Should you wish to make your own, head down to the library and procure one or several of the many toy making books. Most seem to be written in the 1970s before plastic toys and video games. Tool and skill wise, you can make a lot of toys if you have the ability to saw straight. That should be trivial with a bandsaw, but obviously you can also do it with hand tools if you lean towards neanderthal.