In a Pop Photo 2002 ad, they list a black FM2 for $479, chrome FM3A for $459 and a black FM3A for $489. I am certain people aren't bashing the FM3A for it's unique properties more so then the price difference.
Yeah, that was like ten bucks then, now it is more like a $100-$200 difference depending on condition. For example, FM2N's in good clean condition with a bit of brassing go for $150-$250, FM3A's in the same condition go for $300-$380. Put either camera in the mint category and there is less of a difference, about $75 to $150 and often about the same. BTW, I got mine from B&H in June of 2002, it was $525.
The big differences between the FM2N and the FM3A is that there were a *lot* less FM3A's made and they truly are a step above the FM2N or FE2.
The reasons it is a step above is that very remarkable hybrid shutter, an achievement of having a really great step-less auto mode with exposure lock and TTL flash that has it's own dedicated -1 stop comp button. Then....if the battery goes kaput, you still have a fully workable shutter speed range including still being able to sync at 1/250th. The meter in auto by the way is amazingly good, hitting the target with exposures well into the minutes. Shooting tons of cold weather and mountaineering, I indeed have had the battery go and just kept right on cooking. The finder is also noticeably better, being brighter and having a screen that is as good as a Beattie but seemingly sharper in my experience. Another not well known change is how well sealed up the PCB boards are on the FM3A, a move Nikon did to ensure it would not short out due to condensation if taken indoors after being in prolonged cold weather. Lots of improvements were done to the FM3A as a last in the line tribute to a size and build of Nikon that won the accolades of millions of enthusiasts and pros alike. In my direct experience, it's an FM2 sized and styled body that is in another league.
As I said before, it is probably Nikon's most misunderstood and bashed camera by enthusiasts. I have been using Nikons in my career full time for nearly 30 years, the FM3A has been one of the best cameras I have ever used in any format by any maker....I ought to get another one because they are so cheap right now.