I don't really think data size is an issue. I'm willing to bet that the entirety of Elite Dangerous is vastly smaller than your average 50Gb AAA action game. Procedurally generated systems are often quite light. Read a bit about it here:
http://www.jongware.com/galaxy1.html
Now look at the computational power that existed at the time to create/run Frontier and compare to the power you have today as well as the advances in algorithms, data compression and all the other factors.
Edit: Google Earth is massive due to all the non-procedual data. You can not compare that to a procedural system like the FD Galaxy, which draws on a relatively small set of data (textures/models) to populate the procedurally generated galaxy.
You're right about Google Earth of course, it was a bad example. However, Frontier didn't have any sense of a dynamic galaxy. You could scum a trade route forever, and never, ever, ever run out of stock or affect the trade prices. I've seen prices change by over 10% in ED on popular routes (Wolf 562, LHS380, Bunda(?) for example) As you explore the galaxy, the explored systems have to update, the trading and politics of the systems update etc., plus your loyalties to factions in EVERY system. Even if that was compressed down to an average of 32 bytes per system, the database would be 12TB. I work in IT, so that kind of storage these days is pretty cheap from my perspective. £4000-£10000 or so including GFS backup. I spent £21,000 on a system last year with 16TB on a redundant array of 3 servers. Easy. Not the kind of thing a home user could set up though...
Of course, you could assume that the database could grow as you explore, i.e. each "non searched" system would result in an empty search and so just end up procedural until explored or traded in, but you can't work on the assumption that some deep space explorer isn't going to explore and trade their way through tens of thousands of systems in a year, and you still need a database engine that can cope with that running on a gaming PC, which will be less than ideal. You need fast drives, fast memory and fast processors. My servers above have 16GB each, and I've seen them scraping off the ceiling if the load balance is off whilst we're doing merge queries for example.