I thought it was plausible given the accuracy of F9 landings, though I still wonder how it will work at scale if one failure destroys the landing site. That could ruin the cost benefits.
Where his vision hit a lot of speed bumps is second stage reusability. Starship is a beautiful second stage to throw in the ocean. They’ll probably get it landing but the heat tiles will require a lot of refurbishment between flights. They’re going to have to figure something else out.
It took months to more than a year to repair shuttle’s heatshield in some cases. SpaceX replaced the entirety of the heatshield with a new design and a new ablative underlayment in a matter of weeks. I suspect they will be able to do it even quicker with design and process improvements. Small scale repairs of the heatshield between flights probably wont be all that big of a deal.
The fact that Starship is unmanned probably helps expedite the change process quite a bit vs. the manned Space Shuttle. If you want to "just try something" the most you can lose is money, and not create a national political scandal.
I think the problem with shuttle was more fundamental. most of the tiles for Shuttle were custom cut to fit exactly one spot on one orbiter. I've read that NASA replaced about 75 tiles per mission, and that 2/3rds of the cost of refurbishing a shuttle after flight was the TPS. so the cost of trying something out was massive.
I really don’t think it will ruin the cost benefit as much as you suggest, especially when they have multiple sites and multiple locations. It wound be catastrophic, but they are presumably building Tower like the rest of their hardware, and every time they launch it represents a $100M saving compared to the competition.
I'm expecting that SpaceX will have lots of towers, not just one (currently) or 3 or 4 (under way). It won't just be for redundancy. The duty cycle of a tower might simply not allow for the cadence that SpaceX wants to maintain. With Falcon 9 they currently have a 3x weekly launch cadence (which is unbelievable enough). With full reusability they might be able to get to daily and better cadence, so if the duty cycle of one tower does not support that (I assume right now it does not) then they'll need more towers.
A flight to Mars is currently going to require 10 tanker flights just to get enough fuel into orbit for 1 Starship trip. Containing liquid fuel for long in orbit will not be easy.
This likely means they are targeting 10 flights in a day at least. They've mentioned 1000 trips to Mars during one transit window, which means ~10000 Earth launches within 3 months, or >100 per day.
Where his vision hit a lot of speed bumps is second stage reusability. Starship is a beautiful second stage to throw in the ocean. They’ll probably get it landing but the heat tiles will require a lot of refurbishment between flights. They’re going to have to figure something else out.