Depends on the airline, but the limit on overweight bags is usually 75-100lbs. Yes, they do charge you the overweight fee....which varies by airline and total number of bags checked.
Get everything frozen and you can fit a boned out deer, skull, and rack into a large rubbermaid container under 100lbs and check it on the plane. Fill it with soft goods, clothing, etc. for a little insulation. Everything will still be frozen when you get home. I've also done this with goats and bears in August without anything thawing.
One other tip is to compare the baggage and weight restrictions of coach vs. first class on the airline you are flying. First class usually gets more bags, and higher maximum weight per bag before they start charging you extra fees. You can often fly first class for the same price when you are traveling with really heavy bags.