Maintenance on a car that isn't driven can't really be compared directly to maintenance on a car that is driven regularly. Some things wear out MORE quickly when the car is NOT operated (the battery principal among these). Also, one must be careful to keep up with oil changes, other lubrication etc... on a different schedule, and some moving parts have a tendency to freeze in place, seals suffer dry-rot etc...

While low mileage is a good thing, extreme low mileage without significant preventive maintenance tends to lead to its own set of problems. This is particularly true when the car is then only operated for short duration events (which probably doesn't describe most folks here). Add also the hazard of not keeping it in a garage or other protected environment, if you don't have that option.

If you figure out your costs on the car that isn't driven, it might not be as cheap as you initially think, particularly if you look at it on a cost-per-mile-driven basis. OTOH, it is should remain much cheaper on an annualized or monthly basis.