I have a friend with a custom slot car race track. It is designed to fit a specific space in his house, and the entire 4-lane track loop is one huge solid piece. I have no idea how they installed it. As with any hobby appealing to big boys, the cost can go exponential.
As with model rockets, a lot has improved in slot cars since the last time around: high-energy ceramic motor magnets, silicone rear tires, independent front wheel rotation, light-weight polymer traction magnets, separate power supplies for four racing lanes, banked turns, and, of all things, brakes.
Four parallel lanes with various turn radii is a kick. It also has a built in digital timer for each lane, to compound the competitive pressure. The dynamics of guys practicing solo racing vs. four-person competitions follows the Sapolsky rule for baboons:
“When baboons hunt together they'd love to get as much meat as possible, but they're not very good at it. The baboon is a much more successful hunter when he hunts by himself than when he hunts in a group because they screw up every time they're in a group. Say three of them are running as fast as possible after a gazelle, and they're gaining on it, and they're deadly. But something goes on in one of their minds—I'm anthropomorphizing here—and he says to himself, "What am I doing here? I have no idea whatsoever, but I'm running as fast as possible, and this guy is running as fast as possible right behind me… I'd better just stop and slash him in the face before he gets me." The baboon suddenly stops and turns around, and they go rolling over each other like Keystone cops and the gazelle is long gone because the baboons just became disinhibited. They get crazed around each other at every juncture.” (from www.edge.org/3rd_culture/sapolsky03/sapolsky_index.html)
I jokingly call the timed slot car races "baboon races" as over-eager cars inevitably fly off the track in the very first turn...