Ok, I went and took my player apart to look at the button back side to refresh my memory. They can be made straight pull as is. But half of that mold is relatively difficult to cut.

The cap side mold is an open pocket. Relativly easy to cut. The socket side is tougher. Thin walls with notches and a protruding core. All have to be machined using small mill cutters. That, or additional pins (cores) have to be inserted into the mold. More parts.

I think the molds would be easier to make if the button was two parts. Cap and socket. All mold surfaces would be either a simple pocket or a protruding core. Larger diameter tools can be used. Polishing is easier. Easier is cheaper.

This job is really bounded by keeping the front end costs as low as possible. If that can be done by letting the end user do some self assembly...