Give the customer what he wants. But tell him the tradeoffs.
The idea that it would cost 600-800 for 30TB of data is ludicrous. You can't even buy 30TB of commodity hard drives for that. My numbers put it at 2250 with no parity. I guess that if he really wants that, set him up with an rsync...
I'm a recent convert. That having been said, look into Unraid. (google it).
Don't let the price deter you: this is cheaper than real raid, and the characteristics are likely better. I'm about to build two 11tb unraid servers to dismantle / replace a large Raid-5.
Raid-5 is so much...