Is that actually the case? In the product comparison the VPS column has MySQL Databases "Unlimited", the same as for shared hosting. Does a VPS still require you to also have a shared hosting account? You definitely need to pay extra if you want both a VPS and a dedicated VPS for MySQL, but I was under the impression that a VPS account had the same access to shared MySQL as shared plans do, since they use different servers anyway.
Personally I have a bunch of web-sites, but only one that's currently overwhelming my shared host, so I may well run both a shared plan and a separate VPS for the high-volume site, but nothing in the product details or the comparison table suggests that it's required.