I know many people from China also use VPN for accessing many website services and it works just fine, so ''great'' firewall is not that great afteral.
Don't they use residential VPNs for that? I would assume they block any known VPN IP address in their "great firewall".
I remember the days when I ran an open proxy. Without advertising it (it was meant for myself only), it got many Chinese users.
I think that Mullvad is the best VPN you can buy anonymously with cryptocurrencies, but they are certainly not the cheapest available option.
It's the cheapest one I've seen if you don't need it continuously. You can literally pay for an hour, and create a new account when you need it again. I just tested it: €0.01 got me 1 hour and 38 minutes of full speed VPN.