I have no idea where that number comes from. I seem to remember that a naive implementation would have required 10x or so the existing resources (proportional to the characters in the average query at the time... We know they've been getting longer over the years). But that's not at all what was released. Also remember that this is just the serving path. Crawling is not affected, while for indexing...it depends.
My service did not get 7x the resources for launch. We did bring up more capacity, but we also improved things here and there. That's work that would have been needed anyway.
Last but not least, there were infrastructure improvements that helped reduce resources in search and other products. Bob Wyman's LinkedIn page says that his team helped with Instant, but also saved AdSense 100k+ cores, while increasing serving capacity and reducing latency.
As for the value: speed, differentiation and sheer coolness.