while worst case is 175$ (havent checked) best case is free, that means you win the desired item just by the compasses sent to you with mail
i wont the dragonmount this way last pr.card event (though its almost useless for me since i have better mounts)
so i recommend:
you only gamble with the free compass, if you win its good if not then not
for a decent mount try to find someone selling a pegasus / wraith / rumble / manabike (if you have enough gold)
or just buy a griffon which is rlatively cheap and still fast for the gold it costs (and also fast due to its leap)
if you are a mountcollector or something however it will be hard
only thing i can add then is that these mounts will often be sold DIRECTLY later in shop