The continuing dregs of the war and the transition to rebuild Sylvania's infrastructure has probably been very expensive.
Stirland is in a vastly better position to develop than it has been for a very long time, but the amount of available liquid capital it has to pay for imported goods and services that hasn't already been committed may well be pretty limited.
It has a lot of growth potential, but is still probably cash poor, and what there is is probably pretty well spoken for. It may well be prosperous in a generation, but that means it's generating big surpluses now.
And if it does need to buy expensive Waystones, that leaves less capital to invest in the other things that will make it safe and prosperous.
Worth noting that I'm fairly sure that Stirland will get some sort of financial aid for getting Waystones set up, particularly in Sylvania. The Undead coming out of that place are everyone's problem, and untaining that land is something everyone in the Empire can get behind.
And while there will definitely be arguments to be made for places like the Forest of Shadows and such, Sylvania is currently militarily pacified and lacks the problems of trying to keep a close eye on things through a dense and large forest full of dangers.
Extra bonus points for the appeal in the huge incentives and economic potential for the new canal route; untaining that land could foster a major economic boom along a new, major trade lane stretching from Barak Varr (and technically all the way from Karak Azul), going through Zhufbar backyard (and they certainly have a lot of desireable goods to sell and materials to buy), and right into the heart of the Empire.
Worries about the northern Empire being ignored can be mollified by how this project will aim to cover everywhere in the Old World where the land can be relatively secure, and that the northern flanks can't be ignored because one of the most important places for Waystone deployment will be northern Kislev.
Stirland as it is now is definitely not impoverished, but it is probably relatively short on funds. The good news is that it is that way because it has been spending its money constantly on improving its situation in decisive, lasting ways, and successfully so. This is helped by the fact that a lot of the money Stirland has spent has been going into the EIC, which itself has been spending that money building a major economic powerhouse throughout the region, Stirland very much included. That gold spent has been indirectly fueling a buildup of Stirland's economy.
In the long term, pacifying Sylvania, the canal project, and the EIC, coupled with gunpowder/niter production and modest but noteworthy firearm production, alongside the major potential with Zhufbar being a neighbor but now without corrupted Sylvania getting in the way...there is a LOT to look forward to. And when We-silk starts hitting the markets, traffic through the canal will pick up at a dramatic pace.
While the work of truly rooting out chinks in the armor for Vampiric influence to seep through will be the work of generations, it really does seem like Roswita's reign will see the days of Vampires and Necromancers feeling comfortable or powerful in Sylvania at an end. The Grey, Amethyst, and Light Orders will definitely have to keep a close eye on things there, but now they can readily send Wizards to any town or city in that region to investigate rather than needing to have an army at their backs to even get close.