My scheduled maintenance was not included (I have a '98); it has been dealer-maintained and I don't recall that the amounts were out of line, tho if you want precise numbers I will be happy to look them up for you. I think they varied between $200 and $400 depending on whether it was an A or B service -- probably very similar to a normal M-B except when AMG parts like the brakes are involved.
These maintenance costs are not, however, significant numbers [depends on what you call SUPER expensive] compared to, for instance out-of-warranty replacement of a transmission or, in contrast, replacement of a 140 A/C system or destroyed valves after a timing chain failure.
I would not worry about "maintenance" (even for $800 brake rotors -- they are not something you do every 3,000 miles) -- major expense items are what I would worry about. If ordinary maintenance expenses are already a burden, then major expense items will likely break the bank. You can insure against the major items by getting a Starmarked car where the dealer will fix it without a deductible and minimal incentive to jerk you around since the bill goes to M-B -- lease it for the warranty period.
I think that the AMG cars are as well built and durable as anything on the market (I would not, for instance, buy a used M3), but like any "luxury" item you have to be able to deal financially with a catastrophe even if unexpected. If you can't self-insure, then go with the Starmark and stay in the warranty period.
'98 C43 AMG
'93 190E Limited Edition (including factory Sportline package)