Making your own paper wallets might be your most inexpensive method, but you have to know what you doing or it will be your worst nightmare. There are a lot of advice on this forum on creating your own secure paper wallets, so you have to do some research before you attempt this.
Buying a hardware wallet will be a bit more expensive, but it is a lot easier and it gives you easier access to your coins. The other methods < Desktop wallets and online wallets > are the least secure, but the easiest method to store bitcoins.
I got a mail from trezor yesterday, they seem to have dropped their shipping fees within the EU, so a hardware wallet does cost less than $100, wether it be a trezor or a ledger nano S.
That being said, my own view on the topic:
Safest:- hardware wallet: both reasonably cheap and easy to use
- airgapped pc: expensive and a little bit harder to use (you always have to transfer unsigned/signed transactions between an online and offline machine)
- Paper wallet: very cheap and very secure if generated in the correct way, but hard to use (you have to sweep and discard the paper wallet each time you use it, then transfer the remaining value to a new paper wallet)
Medium:- Desktop wallet: free, but you need a clean PC and you NEED to encrypt your wallet (using a strong passphrase). Virusscanners/firewall are a must have
Unsafe-ish:- Android/Ios wallets: I call these ones unsafe because it's harder to verify the wallet's signatures, many people know less about their phone's OS than they know about their desktop's OS, and phones can easily get stolen/lost
Unsafe:- Any wallet where you're not the (only) one in controll of your private keys. This includes exchanges and online wallets
Agree that's a good list, hardware wallet seems to be the most secure, however you can achieve very good degree of security with certain desktop wallet including Bitcoin Core.