What's preventing another competitor from buying self-driving cars themselves and pushing the margins on automated taxis down to a commodity product? Anything

What's preventing another competitor from buying self-driving cars themselves and pushing the margins on automated taxis down to a commodity product? Anything that you need to pay for has a chink in the network effect armor. All a competitor needs to do is price cheaper and all your users will flock to them. Tech companies survive on fat margins, but I think this industry is heading the other way.