I've always felt like flying removed the immersion I felt oh so long ago, but there wouldn't be a good way to rekindle that long dead fire. Flying around in the Outlands just feels right, but I'm unsure about Draenor. Azeroth was built for ground mounts, so it looks good from down below, as opposed to making weird routes over endless canopy and wasteland. Paying gold is obviously going to be part of the training portion, but I think it should have a rather in-depth questline that could be completed in a day at most, to contribute to the cost. I'm not sure about inflation in Draenor but since you earned ~5k in MoP, I'm assuming leveling and the questline will be able to cover the cost.