Your healthy tooth dies, but the good fact for them is that you pay for the whole
process about 3000 zl (extracting the once very healthy root, closing the channel,
canal/channel treatment every week, etc)
If you paid 3000zl for canal treatment then you've got robbed. As simple as that, your dentist robbed you. I've got canal treatment in Poland, it took about five visits cost me 250 zł with insurance, without would cost me 500 zł... It was private clinic. CHANGE YOUR DENTIST! (and tell that thief that he/she is a thief)...