That's correct, but I was interested in a flight, that from WAW to NRT was through Seoul and was joined LOT+Asiana, and rather cheap. This flight is offered only through OTA, that do not give an option to buy 2 pieces of luggage. Thus I did not know, how expensive this flight would get with those 2 pieces. Maybe I was unclear in my initial question...

Anyway, I bought directly through LOT. Coming day later than I wanted, but at least I know the price.