My Mercedes 7G transmission was acting crazy – indie shop fixed it for 1/4 of dealer price

I've got a 2015 ML350 and the transmission started flaring between 4th and 5th gear – revs would shoot up before catching. Took it to the dealer and they said I needed a new conductor plate and valve body, quote was almost 12k. I almost passed out. A colleague told me about an independent that specializes in Mercedes repair Dubai and I figured I had nothing to lose. The owner there said the conductor plate issue is common and can usually be repaired by replacing just the electrohydraulic unit, not the whole valve body. He did the job, serviced the transmission, and charged me 2800. The car has been perfect for four months now. I honestly don't know how the dealer justifies their prices. Anyone else had a similar experience where an independent saved you from a massive dealer bill? I'm never going back.