I did a quick comparison with DigitalOcean, and it looks like equal (obviously, with more features). What's cheaper cloud hosting than DO (that's not crap)?
The big difference is that with Portal you can run 8 x 128 MB (or 4 x 256 MB) VMs within a single 1 GB memory plan. Running each of your apps in a separate VM on a standard VPS would cost a lot more.
Yes, we initially used containers. We think VMs are a more secure form of isolation, which is arguable. We also want users to have the ability to run apps based on a variety of operating systems and kernels.
Portal apps themselves can use containers of course. For example, a game server app might run each game process in a separate container within its own VM.
https://www.vultr.com/pricing/