Although I have bought three great conventional locos from TrainWorld on sale, I guess I am not their average customer.
I have a fairly complicated 10' x 5' layout, with 9 switches, on a very solid custom built table, with 3 conventional steam engines, and three conventional diesels, plus about 25 cars, with foam track underlay, and a Z-1000, and all told, over the past two and a half year, I have spent about $2,800. Except for three of the locos, and the materials and paint to build the table, and the foam track underlay, and the wire, all of the rest was bought used.
And happily, all of my trains run great.
From here on out, I will probably spend about $500 per year. Maybe $250 on my birthday and $250 at Christmas.
I am now in the "add interesting operating trackside accessories" mode, but you can find those used in VG condition for fairly cheap. Most of my time is now spent trying to wire them up and get them operating.
I think that once somebody gets hooked on "collecting" trains, or buying totally realistic scale O, or complicated command control systems, then they are doomed to poverty! :-)
(Not for me thanks!)
Mannyrock