We also rebuild our own transmissions. Typically around $1500 installed and adjusted. We have a whole room full of corse so we never charge more even if large pieces are bad. The get those pices from the cores or we don't rebuild. If we havce one that can't be rebuilt (we won't build one from pieces - too much risk) we get one used.
If it can't be done for that price a MB rebuilt is around 2k (not installed).
Bosch Master, ASE Master, L1
33 years MB technician