when we do that trans pacific flight now we weigh our bags at home on the bathroom scale, not 100 % accurate but gives us an idea. then we repack if necessary... I also think out contingency plans for any bags I think might be just over the limit, like packing books or heavy things right on top so if they need to be moved to another bag or carry on, its easy to do it. Larger suitcases, I put all my lightest clothes etc in because its so easy to go over the limit. The check in staff will make you repack if you are over, or as you say, pay huge amounts of money. I like that some airports now have scales where you can weigh your bags BEFORE checking in, so that you dont get a nasty shock at the check in counter. Dont expect them to turn a blind ey to your overweight bags, they won't do it, and every time we fly, they seem to get more strict about this.