I would probably pay extra for a switch although a big heavy mechanical switch in the middle of the signal path for a modern SSD would probably not be as cheap as you might expect.
It can even be jumper pins the user who cares can attach their own switch to. I'd pay extra for a slide switch on a USB stick. Heck, USB sticks often come with a slider for a retractable cover, obviously that cost is insignificant.
Hard drives used to come with those jumper pins. They are not costly.
The point I was making is that the signal integrity work would be a lot harder than for a hard drive of yesteryear. The BOM cost of the switch isn't that important
