P4 ---> 110 fuel done and done
If you make p4 cheaper you would have to make T3 more expensive. And that is not going to end well for ostheer, especially considering p4 is not the obvious choice. Also when you think of the fact that you usually don't build more than one and never more than 2, I would rather consider lowering building price and increasing p4 fuel price as a needed ostheer versatility buff.