Now that the Frogskin and Jacket designations are going by the wayside, it's harder to say what constitutes a "budget" frame. One of the criteria that was a staple of the old system was the use of Unobtainium. Frames that had it were more expensive than those without. Which puts Dogs, BottleCap, Gascan in that bracket (and Riddle?).
Instead, I prefer to look at the frames in terms of use. Some of the fashion-oriented frames (Gascan) are fairly cheap. But so are some of the more general-use frames (MD). But, the more athletic frames (HJ, RJ, WJ) are pretty pricey.