The fee is correct given what the OP stated, here is the rules from aa.com:
You’ll be charged the checked bag fee of your destination and the following items will be treated as a single item:
- 1 pair of skis
- A snowboard
- 1 boot bag with only boots/bindings, helmet and life preserver
Your boot bag can be up to 45 inches (length + width + height) and must contain only boots/bindings, helmet and life preserver.If you put anything else in your boot bag, you’ll have to pay an excess bag fee. You may be asked to open your bag at the airport.
When you’re traveling to, through or from Brazil, once you’ve used your free bag allowance, your ski equipment will cost $28.05.
The bag according to the OP contained 2 snowboards a pair of skis, poles, and one pair each of ski boots and snowboard boots, plus a few miscellaneous items like ski gloves and pants. So while yes there's no weight listed for allowable bags for skis or snowboards BUT you are only allowed 1 snowboard/skis and that's all. Sounds like you had 2 people gear (snowboard and skis) in the same bag, had you put them in separate bags that would have worked. Also FWIW I've never had any issue with my bag that has all my gear (pants, jackets, undergarments, helmet, etc) but also its ~65-70lbs and thus under the 32Kg/70Lb limit allowed for EXP. My guess is being over 70lbs is what did you in, also will point out in case you ever ride outside the US that many countries have hard health and safety limits on checked bags and will not accept anything over 32Kg.