Depends on what someone is willing to pay you for it. Personally I dont buy cards only trade so to me its worth any other prime card you would want i nexchange for it.
For the record though I have bought two cards, once we bought a Rayquazza EX Delta bwcuase we were in a shop in Canda for a City CHampionship and my wife wanted once for her deck. I also pught a Pachirisu GE card in Oregon from BDS becuase it was like a quarter and my daughter asked for it.
My wife once baught a base set CHancey online for me for Christmas the first year that pokemon came out. But in 13 years of Pokemon that is all I have ever purchased.
its really hard to speculate prices when the card has JUST come out. Wait 3-4 weeks for prices to stabilize. They can go up or down depending on if it does successful in tournaments, someone "breaks" the card and posts an amazing list online, supply/demand, etc.
I personally think the card will go for less than $10 in the near future.
He was on your side of this argument before I furnished him the evidence
$5-7ish now because of speculation, potential, and as you can see doubters. If/when Lost World is ever confirmed for an English set $25 will be cheap before it's all said and done.