I didn't make the list to add up to 50, I just copied the list someone did on wowhead and edited it for more accuracy. Also some of your costs are incorrect, I believe both Netherwing and Skyguard mounts are 200g each, as are the normal epic flyers. Normal flyers are 100g. Level 30 mounts are 10g, 60 are 100g.
The actual price is 4,430 gold before faction discounts, not including the cenarion mount. Other races could remove all of the 200g mounts and the cenarion mount and save ~2300 (4300 including hippogryph). Albino Drake is decent, but like others I'm sure I will be going for the proto drakes from the raid achievements, because not only are they not a huge money sink, they will be much rarer than other mounts (and 310 speed).