In addition to that Sightseek, breeders usally take a wait and see attitude with sires who didn't run to their breeding. By that I mean those who showed traits not associated with their sire lines.
El Prado is just awesome as a sire but is predominantly associated with grass and route horses with little speed.
Medag was just an awesome horse, and he showed such a love for dirt and had very good speed, but hes about the only El Prado who ever did. That causes people to wonder if he was just a "freak", and freaks rarely reproduce themselves. They most often revert to siring horses more in line with their breeding.
I will tell you this though, If Medag has a good first couple of crops, and does in fact sire horses with speed who run on dirt, there is no limit as to how high his stud fee could end up being. Hes probably the stallion I see the most with "the skys the limit potential" if his first few crops work out ok.