6GB doesn't sound untenable if one were to store map/graph data in some optimized text or vector form, rasterizing tiles as needed with a cache mixed in. Maybe keep the 20-mile tiles hot all the time... I guess this depends on the geography covered and use case though.
Still, think of the expense. Plus you need at least second for backup. And probably a whole bunch of them in production to handle many users. Think about the web in 1997, before "scalability" was even a word.
