StartSSL will let you do a multi-domain wildcard cert for $75 for 2-years (with identity verification). You toss all of your root domains on a single cert as wildcards, and use it everywhere. Cert lasts for 2 years and can be updated at any time to add new wildcard domains to it. You could in theory get 4 years out of it by adding a domain on the last day if your identity verification 2-year cycle, which refreshes the 2 years on the cert.

I use this method and it is awesome. One big multi-domain wildcard cert for everything.