My recollection is that, from 1992-ish onwards, traditional 2400 and 1200/75 modems actually became more expensive than 14k4.

The reason being that the older standards were used for specific enterprise applications (eg. travel agent viewdata required 1200/75, remote data reporting often ran at 2400) and generally used the most expensive branded modems (Hayes, Microcom, Multitech/IBM).

It was the vendors in the tier below that (Telebit, Supra, USR) that drove the increasing baud rates (often ahead of standardisation) - and it was their products that the no-name vendors cloned and sold at bargain-basement prices.

The difference was pretty huge in terms of user experience. At 14k4, your typical Apogee game was easy enough to download on a whim, but if you were stuck on 2400 you really had to want it.