Revving when hitting the gas while underway is not a good sign, shifts should be firm and the rpms should not rise more than 100rpm when in a given gear with power level increased (normal level of torque converter slip), more than that means internal slipping of the transmission. I'd price it accordingly. A very very nice 190e 2.3 is worth barely $2k or less with a dying trans....at least that's the most I'd ever pay if the rest of the car was excellent.

For reference I paid less than 1k for a 1993 190e 2.3 in pretty good shape but needing an engine replacement (had new rebuilt trans)

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