As far as I know, they worked on the B-58. However, on the XB-70, one out of two capsules failed to work properly following a mid-air collision with an F-104. The result was one fatality and the other guy was injured pretty severely if memory serves.

Those capsules would end up costing many times the $50 per seat you'd be willing to pay. First of all, they're bulky and heavy so a plane couldn't carry nearly as paying passengers. Off hand, I'd guess that a plane like a 747 couldn't carry more than 150-200 passengers with those seats. That alone doubles the price of a ticket since you've halved the passenger load. That only begins to cover the extra costs. First of all, the ejection capsules would have to be purchased, adding several million dollars to the price of a plane. They also have to receive maintenance, so you'd need more labor to keep the plane operational. Then you'd face the liability issues if some of the capsules didn't work when needed like what happened with the XB-70. Not only that, but can you imagine the pressure on a pilot struggling with a malfunctioning plane to decide when or if to punch out all the passengers? Nope, not going to happen.