Chris,
Not that it helps you any but what you paid for the truck, radio, mill, lathe, etc. has nothing to do with what accessories for any of those things cost. Lathes in particular (and the other items to some extent) don't generally sell well as complete units. Too hard and expensive to ship safely and too cheap for most people to be willing to pay what the shipping costs). Anyway, lathes are cheap. Accessories usually aren't, in part because they sell well. You might find a QCGB for $200, but not on eBay. The average there is about $450 to $550.
Unless there is something wrong with your existing lead screw, you do not need another one. All 12" Atlas built lathes with 3/4" lead screws built from 1940 through 1967 use the same lead screw and RH bearing. After 1967, the lead screw changed slightly but the earlier version can be easily modified to work (shorten and drill one hole).
Robert D.