I honestly think removing the iron sight shouldn't cost more than $60. It didn't take me more than 5min to install and center new irons onto my XD Mod2. Having the slide milled or cut for optics is a different story. That takes Precision and time.
The closest gunsmith near me will charge $120+ for small things like adjusting trigger pull or sight adjustments. They'll even charge $80 for lubing a gun you asked for appraisal on top of the $100 appraisal fee. I didn't ask them to lube a rifle that was already cleaned and lubed.
Either look into a $40 sight pusher or ask around for a quote. Maybe haggle on a price.