Actually, it is more like, good personnel is hard to come by in Starfleet and the KDF (most people would rather stay at home and play holodeck MMO's), so anyone who is willing to work is really, really appreciated. By "buying" people from the fleet starbases or the personnel officers is actually giving those people money so that they even apply to the job that you offer.
They still get a salary and everything from Starfleet/the KDF, of course, but that is not the individual captain's problem. Trading people on the exchange, however, is just the captains having established some way of exchanging the highly-sought personnel. Of course, syou still have to convince those people to accept the transfer, but as we are all savvy captains, we just manage to do that.
Ships? The boxes contain not the ships, but the command codes and paperwork, of course - or in the case of shuttles, the material and energy credits required to replicate one.
I did feel kind of strange turning in my winter epohh's to the GPL converter. Almost felt like I was putting a living thing in a microwave or something.
What do the Romulans DO with them? Attach them to large wooden polls and use them to scrub singularity compartments? Somehow cause them to become plasma and fire them at other ships? Perhaps... finally... we know what they brew Romulan Ale out of.