I can see an argument for this for Tesla, because of the capital costs. I can see an argument for this for Uber, because of the network effects. But I cannot see an argument for this for Google Photos, because the network effects are not that strong, and the capital costs are directly proportional to how many users you have. (You don't need to scale our your datacenter/cloud until you actually have users to justify doing so.)
So while I agree this can be an issue in general, I'm not seeing the argument for it here. I think it would actually be relatively easy for a competitor to get started in this space.
I think you're underestimating the cost of leaving Google Photos.
Sure, it's not too bad but I need to migrate off a new platform literally 5 years of photos (+ face tagging), explain it to all my relatives, make them install another app.
Or I can just start paying 2$ per month.
I'm not too bothered but it's a clear bait and switch.
To be fair I wasn't sure if this was coming or not given Google is not exactly a small business and could afford to spend some storage money to lock people in better in their ecosystem.
So while I agree this can be an issue in general, I'm not seeing the argument for it here. I think it would actually be relatively easy for a competitor to get started in this space.