Same here, the cost is just way more worth it if you already pay for other Proton services.
Does seem like IVPN is closer to Mullvad in how it works though for people who just want to pay for a VPN separately. No email needed for an account, similar price, open-source clients. Also debubks misinformation used by VPN peddlers to convince people to buy VPNs who don't need one.