I store my seeds locally in fire resistant safes, and tucked into fire resistant document bags. I have three safes on the property with redundant backups. The odds of all three burning up to the point of all backups being unrecoverable is pretty slim. My brother and I have talked about each buying a small document safe to hide in the other's house for redundant off-site backups, but neither of us gone to such lengths as of yet.
I've never looked into a safe deposit boxes, so I don't know what they go for in my area but I can't imagine they're cheap. A small
document safe built to be fire and water resistant can be found for under $175. Even if you had to buy two to have redundant backups in different parts of the house, that's still pretty affordable. Again, not knowing the cost of a safe deposit box, I don't know how that compares.
Oh, this eternal headache with the organization of safe storage of seed phrases. Apparently, this problem will exist all the time as long as crypto exists. On the one hand, this is a great advantage, on the other, a great responsibility to oneself.
If someone really needs it, then without any difficulty they will open this safe (in principle, any). For the most part, this is protection only from petty hooligans.
The $175 safe is a carry-on, so you need to mount or buckle it up. At a minimum, so that attackers spend more time and make it easier to find them.
The solution with a safe deposit box (or other storage locker) is rather dubious, even if only part of the information is stored in them. Additional backups will be required here, in case access to the cell is lost (for example, due to confiscation or theft). It is rather reckless to consider a safe deposit box as the main place for storing a phrase. Why do you need the unique opportunity to personally manage the seed phrase if you leave it in the hands of centralized systems? It's like storing crypto currencies on exchanges.