I would add only that it isn't polite to call them unreasonable - just that the offer is not realistic. It's a fact that increased responsibilities demand highe

I would add only that it isn't polite to call them unreasonable - just that the offer is not realistic. It's a fact that increased responsibilities demand higher compensation, and you shouldn't have to explain that to them. Make a counter-offer: "Considering the added responsibilities and my extensive experience in the field and within the company, I'll be happy to take the position for $AMOUNT."