+5 cost per increase will be removed, dev efficiency not affecting whole cost is a bug and will be fixed. To balance the lack of cost increase for repeatedly developing same province, we'll make it so you can't develop any one of the three values to be higher than the other two together (so you can't make a 40 production 1 bt 1 manpower silk province).
I don't agree with this choice for a number of reason. I understand there are a lot of people complaining about development costs. I have seen that in my europe nation games, however if playing on different parts of the globe there are other concerns. I haven't done an Americas game yet, but for the others there are a number of issues across the board:
1) If development is made even easier, AI nations will go even taller, increasing annex/coring costs - that will make building a wide empire even harder than it already is. Will there be something done to fix that? I read somewhere about someone that had a 3k piplo annexation cost, I saw a 1k cost in my game for a 5 province vassal myself, and the provinces weren't that developed.
2) Restricting development relative to the other factors makes somewhat sense. However I see this negatively affecting gameplay, especially when playing a less developed nation - you need administrative to core your new conquests, you need every single bit of mil power to put inside mil tech to keep up with strong enemies - so the last obvious choice left to develop countries is diplo, which I was gladly putting into my poor provinces to boost my nation to be able to compete - restricting this would mean one would definitely fall behind in military tech playing a poor nation, as you're now forced to spend all monarch points on development, not just the ones of your chosing.
Though it is probably a good thing to get rid of the +5 per increase, I'm worried about the AI's reaction and the new restriction.