I took a look again at casa's offering, and they do talk about doing it yourself.
https://docs.keys.casa/wealth-security-protocol/casa-vs.-alternatives/option-1-do-it-yourselfSo they have a free option, and some paid options, and the most expensive one is that $5000 per year one, designed for people who probably hold $1m or more of king daddy, and don't want to bother with setting up their own private ranch to store one of the keys to their coins. Remember it's a multi-sig wallet.
I believe this is easily done using 2-of-3 multisig as a minimum, and you only need 1 other device in addition to the one you normally use. People who don't use multi-sig probably have either a hardware wallet, or a cold wallet configuration set up using some air gapped machine. This can be an old phone or old tablet (or even a new one) used for just this purpose.
For my own use case, I got a cheap tablet, nuked it, erased it, kept it offline, and copied over Electrum from another offline machine. Now people are going to ask if I physically disabled the wireless connections, but I didn't do that. I just never connected it to anything and it's on permanent airplane mode, most of the time the tablet is actually turned off and stored in a box. I don't have the amount of coin that would warrant more security than I have now. I may consider upgrading my own protocol when I get to that point, but for me, no one else is going to be able to touch my coins.
There are a few people out there using Bitcoin Core and Electrum with both a watch-only wallet and a cold wallet for signing.
It's a trade off between security and convenience. Tapping your debit card is convenient. Inserting it and typing a 4 digit pin code is inconvenient. Pushing lots of buttons and digging out cold storage from where ever you hid it is annoying. It all boils down to the user.
Some people are willing to pay $5k a year to know their coins are secure. I'm not one of those people, but if I had a friend who had a couple million dollars worth and I know he's not very technical, I'd suggest to them to take a look at paid services (or I'd offer my own service to him, teach him how to do it himself, get him a safe deposit box, etc etc etc; pay me and I'll keep our coins safe.)
You could pay Casa the $5k for just one year, and try to do transactions every month. When you've learned how to do it and what they teach you, because they supposedly teach you how to access your coins in the even the company completely disappears, you use open source software, then you could try doing it on your own after that.
At the very least, they have a lot of knowledge that is available for free, so everyone can do it themselves.