I already have one full archival node, and many pruned nodes. The cost is not the issue in case of local node, the problem is you usually don't get hardware with built-in 4 TB disk, so you need some external one. And then, OS can do some optimizations to turn it off, when it is not used, and then you need to reindex your full node, because of corrupted database, when Bitcoin Core is killed by some I/O error.

Also, if you have any server, running 24/7, then it is not one-time-cost to buy some larger disk, because you pay monthly or yearly for that, so it is a cost, that will force you to pay more, for a longer time. Which means, having 4 TB of storage on your server in the cloud, will eventually be much more expensive than having 4 TB of local storage, because you are not the owner of that disk, but you pay for a service of having that storage, and then it quickly becomes more expensive than buying a disk and owning it.