Nico Nico Nii!~
Huh. There's a high chance most of those holos are reverse holos of commons and uncommons, so $50 would be a decent price if you're looking to sell them quickly. If you have a lot of ex Pokemon or Lv. X Pokemon, those may be worth something individually, but then you'd probably have to sell all the commons and uncommons as a single lot for $15.
Commons and uncommons are the cards that have a black dot or a black diamond next to the set symbol on the bottom right corner of the front side of the card.