There is nothing more expensive than a cheap Mercedes
But in all honesty look at a mid 90s W202. Would fit your budget with just about enough modernity in them. But parts are pricy and no guarantee if they will be trouble free, but 1.4 million should give a good condition one.
You also in the range of the early mode W203 but those arent known as the most reliable nor well built Mercedes during the malaise era Mercedes had in the 2000s