Exchange price for a key is usually in the 1.2-1.4M mark. So they'd have AT MOST 45M ec to spend. Never mind "get any of the lockbox ships other than the bug ship", I don't think there is one lockbox ship you can buy for 45M ec, excluding Mirror vessels and the Tuffli (which isn't technically a lockbox ship anyway).
I do agree with the sentiment that buying Z-store stuff to resell is the most cost-effective way to get a lockbox ship on average, but you'll need considerably more than 30 to get anything worthwhile (unless you have very good timing and pick up an "oops, missed a zero" bargain ).
I bought 2 Temporal sci vessels a week ago for $40 million each. They were $100 million when the boxes came out same as Recluse carrier - but if you wait a month or 2 they usuall drop in price by half.