The price tag of a chiller is high, but with a larger reef system - I assume it's a reef since we are talking about lighting, skipping one to me is akin to buying a house so big that you can't afford the insurance. Buy a smaller house.
They are so commonly skipped, I can't do anything but shake my head. What do you do when your home AC unit goes out? Perhaps not so much a problem in Indiana, but when you put the cost of a chiller against the cost of replacing your livestock, it's a no brainer. The chiller on my 180 cost me about $1300 to buy, but I probably have several times that in livestock in the tank, including some particularly rare and hard to find pieces. No brainer.