The points you make are all true until they are not. Many useful robots should be able to work well enough for the purpose at a reasonable cost. Part of that is mass production brings prices down.
The problem is of course until we can solve the problem of making it work at all price isn't a consideration. You can go bankrupt advancing the state of the art which then is enough for someone else to take your work and (repeat the bankruptcy part many times until someone works it out), and finally someone makes a ton of money with their useful robot.
You're right, but also software is weird. The world is absolutely littered with good computers that other people have already paid for, just waiting to be put to use for your project to expand their capabilities. If every new web app required its own little pocket computer to run, that you had to convince your customers to buy and keep in their home, it would be much less profitable to develop web apps.
The world is not littered with idle, high-performance robots waiting around for your motion planning algorithm to kick them into action. That makes it a lot more expensive and a lot less profitable.
The problem is of course until we can solve the problem of making it work at all price isn't a consideration. You can go bankrupt advancing the state of the art which then is enough for someone else to take your work and (repeat the bankruptcy part many times until someone works it out), and finally someone makes a ton of money with their useful robot.