You need to buy support on a per-account basis and if you're doing something complex enough with AWS you'll end up with multiple accounts for each environment and for security segmentation etc.
They'll give you general information from your account with the support plan but can't investigate any resources or logs without you owning a support plan on the other account and opening a ticket there.
Also, many companies will have this set up on each account and hardly use it. I don't think it's a loss leader.
Work in AWS Premium Support. Given the sheer volume of accounts with support plans, I'm confident it doesn't lose money in aggregate. Premium Support isn't where you'll find AWS's giant money printer, but it's not losing money.
That being said, I've definitely had cases where the engineering time to solve a case was worth more than that specific account was paying for support (at least for that month).
They'll give you general information from your account with the support plan but can't investigate any resources or logs without you owning a support plan on the other account and opening a ticket there.
Also, many companies will have this set up on each account and hardly use it. I don't think it's a loss leader.