Just did an oil change and 40000 mile transmission service at my local MB dealer.
Just bought my 08 ML 350 last year and i did these services which came up to a total of $730.00. Did i get robbed?

Well, the transmission service isn't cheap. When I bought my car a couple months ago, the dealership showed me the receipt from Calabasas Mercedes for doing the tranny service and it was $462.97. A Service B would cost something like $300. So you paid the average.

I think you got mugged, robbed, and beaten. 400 for the trans job and then a 350.00 oil change, ouch! Service A is fluff like lube the door hinges and top off the wiper fluid, inspect the air filters....blah blah. You can negotiate just the oil change next time and they will reset the service reminder.
You can save a fortune doing it yourself and also reset the service reminder.

A few weeks ago I paid $89 for oil/filer change at a MB dealer here in CA. So it depends what else you did to reach $730

Neither of those things is rocket science. Neither needs Mercedes' diagnostic computer. Any competent indie mechanic can do both. My last service B cost $180 all-in; dealer quoted $350 (and that before taxes and before they add on all those "shop supplies" and the like).

I agree if he/she was going to an independent Mercedes mechanic, but this is standard dealer pricing.

Personally, I'm a complete cheap *** when it comes to this stuff, simply because I know what these things should cost. However, I've dealt with SEVERAL different shops and when it comes to a Mercedes, no one is like the dealership. You must also consider the amount of oil a Mercedes engine requires(~9 quarts), that in itself is almost $100 in oil. Also, if something is to happen, I can throw the car back in the dealer's face and say fix it!