I do believe whoever has over 500K themselves is NOT going to want to dump another 15-20K to level Engineering, and then spend another 30 days after reaching max eng level just to make a mount they could have bough for a fraction of their gold. They would also need to farm/buy more Ore to make Bars, and on top of that either spend a large amount on the 30 Living Steels as well. Also, if they plan to go back to their original profession that is just a HUGE waste.
The only way this mount doesnt sell for over 100K+ is either your realms economy sucks, dupers on your realm, and/or people who just do not know how awesome this mount is going to be.