This should've been posted in the Scripts & Pop-ups forum, not Developer Forum.

When this is in the Remote Tab of your mIRC, you have to get someone else to issue the command, you can't activate your own ON TEXT events

Also, I would change the code so that the item doesn't include !price (which with your code it does)
Here's a suggested modification:
 on *:text:!price &*:#:{
var %item = $replace($2-,$chr(32),$chr(95))
.msg $nick Price of $2- is $readini(prices.ini,Prices,%item)