I don't know how clear cut this reduction in robotaxi revenue is for 2 reasons - 1) the time lag to get 100m robotaxis on the road, and 2) the change in demand for a robotaxi like service.
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so long story short, the combination limited supply and increased demand from both substitution and market expansion makes it seem fairly straightforward that there's time to recoup the current costs of robotaxi and potentially far more before market saturation eats away returns.
The 100 million number wasn't mine. It was from the poster I quoted. I believe Tesla will out compete most private Tesla robotaxis long before that.
It's anything but straightforward that there's time to recoup before saturation. All it takes is that FSD isn't ready for fullblown robotaxi in a couple of years yet. Let's say it's ready in 2025. It could be faster but there is certainly no guarantee of that. It could also take longer. In 2025 Tesla will make something like 4 million cars. Let's say they decide to put half of those into their own robotaxi fleet. After all since it's so profitable why wouldn't they?
Three years later there would be 4+6+9=19 x 50% = almost 10 million Tesla owned robotaxis. You are no longer getting even 12 hours use out of yours. You are likely not getting eight hours either. If you are also using it for your own rush hour transport and only have it available other hours you are probably down to less than six hours already.
Also, you may have gotten a great price for FSD. But there will very likely be a fee percentage just for joining the Tesla robotaxisystem so you can get passengers. Tesla will likely set that fee just high enough that you get to make enough money to continue but not low enough to let you make these several tens of thousand a year many seem to think they can make indefinitely. Why would they?
So you can make some money having your private car you already need/own in the fleet. But so many seems to have a plan of owning several Teslas. Then you need financing. Good luck finding a bank that will let an average Joe borrow most of that money for a second or third car. So you would have to sell Tesla shares to finance.
Yes, if you paid 15k, or less, and you can start using it as robotaxis in say 12 months you will probably have a couple of years with great returns. But so would keeping that money in shares do. Without all the work and risk of delays. Unless it's a car you have paid for anyway the investment will be significant.
No matter how you look at it. When robotaxis becomes a thing Tesla shares is likely to make a much better return than selling $100k of shares today for a couple of years of unknown returns. And you would have to put zero effort into the shares. Except the time spent here.