Excess baggage for a plane trip is very expensive. One way to avoid that is to make sure that your baggage conforms with your weight allowance. For the hand carry bag, only 7 kilos is allowed. You can weigh your baggage right on the check in counter if you come early. It is also good to bring an extra folding bag so you can sort out your baggages, the check in bag and the hand carry bag.
I always usually avoid these expenses by packing my bags with only what is really needed for me during my trip. Nothing more than that (because in my opinion, it's useless).
I had this issue when I had to cancel my rail ticket on account of cancellation of trains. I had to book a flight but the luggage was much too much To my good luck I met an acquaintance who was travelling just with some hand luggage. I checked in with her and all was well.
I generally travel with airlines which allow 30-50 kg check in luggage but I have also traveled with budget airlines which allow only 7 KG cabin bag and if you wish to carry extra baggage you have to pay extra for that. The golden rule is that you get your luggage booked at the time of booking otherwise if you book at airport you will have to pay lot more than what you pay otherwise. I always book luggage and meals at the time of booking.
I always travel light, but there are times when 7 kgs is not enough. One thing I have done if I'm carrying clothes for cold weather, is just put on everything I can (mostly sweaters or blouses) and that usually helps. Other good thing is not every airline weights your carry on luggage, so I guess that has helped a bit!
You are right Alexandoy it did happen to me to pay a huge sum for my luggage. Now that I know this I am taking fewer things with me than before and I don't pay for my luggage when I know that I will buy things from another country I don't take any baggage with me so the cost will be zero!
You are right, in most cases you spend more amount for carrying things which you can buy new at even lesser price than what you paid in form of extra luggage. But there are certain occasions that compel you to bring things which are not available in other countries. Like we had to carry certain utensils like pressure cooker when we first visited Australia and my wife's medicines (for longer period which were not available here in specific salt combination). However, it's wiser to carry the lowest possible luggage and buy it from local market.