Large VFX facilities can't live off large VFX blockbusters, actually. These are taken on for the prestige. Large VFX blockbusters likely cost a VFX facility to be a part of. Yeah, they're expensive, but not for the studios.
Success in the VFX business is breaking even. You can extend this to success for a vendor in Hollywood is breaking even. Historically the bigger facilities not subsidized by giant corporations or otherwise not bound to the same financial pressures as a standalone facility (ie. Sony Pictures Imageworks and ILM, companies with higher overhead than they bring in) have to keep their doors open by taking on work that's actually profitable.
Both R+H and Digital Domain, prior to recent problems, had their doors kept open by having a very active commercials division, with a separate staff from features. DD would have shuttered its doors after Titanic, most likely, if it hadn't been for the profitability of its commercial division. R+H as well was kept afloat by this business which allowed it to take on feature work. Sony has tried repeatedly to get rid of Imageworks because it's a money sinkhole with no chance of being profitable. Lucas too, once he started to ramp down his interest in making more films, packaged up ILM, moved it to the city and started looking for potential buyers, because even they are more overhead than they can be bringing in.
VFX for motion pictures has pretty much always been a bad business to be in if your idea was to generate revenue. And so everyone is looking to create their own content. Perhaps a trade organization will improve things but it's pretty clear that content ownership is the only way to actually do better than squeak by or luck out and have a good year in the black.