Actually that makes a lot of sense. Giving a sort of voucher for a well-developed ship RP towards larger vessels.
Make it apply to anything ship of say 100 million or up. Now you've got incentive for people to play some of the more expensive ships with an actual RP, including things like high-end transports, Liners and yes caps. Expensive weapons and armours will still drive the economy.
The idea here is a monetary incentive to creating an RP. Not a bribe so much, but I'm more likely to bother getting a 5k or other high up transport with this. And if I've already gone and written a story for it, I'm more likely to RP the story than see the ship as a means to something else I want to do on the server.
Only problem becomes implementing it. Probably best would be to have a set of fairly easily applied criteria to award a certain % base ship cost. Judging becomes an issue, but with a well developed set of criteria should be fairly straightforward.