I never understood why people get offended by this. I've seen my share of topics on various sites where people were getting judgmental at scripters for asking for compensation, or because they had the nerve to do commission work.
Whether or not you agree with them selling their work makes no difference, since they have the right to do so. Whether or not you agree the price is right or ridiculous makes no difference since they have the right to set their prices.
What you can do (as others pointed out) is decline the offer and then see if somebody else is willing to do it for less, if not free. It makes me wonder if the entitlement attitude I've seen from some people is driving scripters away.
Also, most scripters make plenty of scripts for non-commercial for the public to use. Some (such as Yanfly and Tsukihime) have even been kind enough to allow commercial use on various scripts without payment.
If they decide to sell some of their scripts instead, or charge for taking on requests, what right does somebody else have to tell them otherwise? Either make do with the scripts that are free, pay up, go somewhere else, or learn to script yourself. It doesn't get any simpler than that.