I think that brigs (blockade runners) should cost less war supllies and more money.
why =
1) to have a real choice to either do some (costly on war supplies - but permanent increase if succesfull) industrial development - or - to work with blockade runners ... now blockade runners are so expensive towards war supplies - you should be crazy not to invest in your industry ! For sure the industrial gains are permanent, and blockade runners in the blockading box will get destroyed one day sooner or later. And those things cost already much war supplies - blockade runners often don't meet their pay back time. So for the moment this is a no-brainer.
2) goods from blockade runners were so expensive, and blockade runners often were "captains of fortune" that used their own ships to operate. Perhaps the CSA goverment constructed a few of these blockade runners - but the "bulk" were captains of fortune IIRC.
So my proposal = less war supply cost - and a higher money cost.