I can get locos and track pretty cheap. Decals, painting, chassis mods, and god forbid I run into something with the running wheels...
If only I could use all my frickin' HO scale trains.

Yes, but that's the gauge of the track, the distance between the rails being 1 3/4 in. The G scale structures (buildings etc.) are another matter, these being roughly 1:20 (or 1:22 depending on who you ask) and this is why some XD fans use Pola G scale buildings for XD diorama purposes, it's reasonably close to 1:18th. The "scale versus gauge" thing can get very confusing to say the least.G gauge is 1/32 IIRC