u/Full-Scallion9041

So ive been sitting on this card for almost 2 years and I can't really find any comps for it I don't intend on selling or trading it anytime soon just wanted to know if anybody could tell me how much I could value this at (autograph is top right corner)

I bought a gold pack on arena club when I first purchased it was maybe pushing 150 i recently checked on ebay recently sold its rocketed up to almost 500 bucks i got the slowking plus 2 others coming in the mail I was just curious why did this card suddenly jump up in price?