In reply to Dollar Symbol / Sign ... 2 vertical strokes or 1?:
The hip hop fantasy of wealth is very rococo; more is more. It stands to reason that it would reject the form of the symbol with fewer lines as not fancy enough.
Advertisements may be the flip side of that. They'll use every trick possible to make something seem like a better deal; they may have hit upon the idea that a simpler dollar sign psychologically looks cheaper.