Looking at the spell tips and patterns from the front page, it appears as if the individual mounts will cost 5x Golden Sink (gotta love the play on words here). Each costing 25k for a total of 125k per mount and making the amazingly expensive Jeweled Onyx Panther cost a mere 500k.
If this price holds till release, I cant wait to make one they are going to be very rare, not many people are able to make this sort of gold leaving it to the goblins
On a seperate note, im thinking that they may need to increase the gold cap if they are going to have these sort of high value items available...