If I have anything resembling a strong opinion in this area it's that convenience should never be gated. I can respect the view that flying shouldn't be possible in Pandaria because you actually enjoy the game less with it. I disagree but that's fine - it is a polarising subject.
But if you take the view that flying is an improvement, don't withhold it from anyone. To motivate players to keep playing by dangling a less inconvenient way of playing in front of them is awful design. I've taken many breaks from wow and the first was when, many years ago, I realised how much I hated levelling through the thirties only so I could continue levelling in a slightly (very slightly) less painful way at 40 (at least I didn't have to farm gold for my alts).
Cool-looking mounts and armour and other prestige items should be hard to obtain. I'm completely in favour of having players' achievements stand out (e.g. real legendaries that look badass from a mile away, full tier gear being a rarity, LFR dropping blues with inferior visuals compared to raids). But convenience and quality of life items should be baseline for everyone. So 10k gold is way too much. Flying generally is too expensive - making a new player (they exist, albeit not on these forums) save up for 280% flying is wanton cruelty. Master flying should cost about 1k and then 100g per expansion. The game absolutely needs gold sinks. BMAH is a move in the right direction - making convenience items like transportation, storage etc a gold sink is very outdated thinking imo.