Upcharge for Ice!

Went out to dinner the other night and ordered a Macallan's on the rocks (sphere of ice). Dinner and service was outstanding but when I got the bill I noticed a 3.00 charge added to an already steep 16.00 charge for the scotch. Is this common? This wasn't in New Orleans but on the sleepy northshore. I get that bars and restaurants may pour a little more for neat or on the rocks than what's generally poured in a mixed drink but I feel like 16.00 has that covered? Inb4 "Sorry to hear about your upcoming bankruptcy"