Sheesh, that's a LOT of dough for a transmission. Early in the life of the Mercedes 722.6 five speed automatic, they had some defects and were failure prone. The cost of a new transmission, converter and ECU was close to $8K, with parts, labour, etc. I thought that was outrageous.
BUT, if you were unfortunate enough to have it last until the warranty was out, Mercedes would sell you a rebuilt (and updated/upgraded) transmission for ~$2500 installed.