Warning: salty language.
Question: are microtransactions euvoluntary? Coercive? The psychology is similar to addiction: tease players with a little shot of dopamine just out of reach, then charge them for the pleasure of fulfilling an artificial goal. The early egregious examples of DLC shenanigans were patently absurd (functionless horse armor in TES IV), but as this video demonstrates, developers (ahem EA) have turned the corner, turning microtransactions into devious exploitation devices.
And, correctly, Nerd^3 echoes Tullock. To avoid getting caught in this web, don't start playing in the first place.
Is there good, properly euvoluntary microtransactions? Sure. Add-on campaigns fit the bill. The DLC for Borderlands 2 is a perfect example. The DLC for Bioshock Infinite would also count if the doors for Burial At Sea Part I weren't broken (but I digress).
There's almost certainly no single perfect business model here. It seems to me that game developers are prone to the same sort of heuristic errors that plague the rest of us. Think of the above video as evidence of supply-side bubble formation. Wait for the worm to turn, people.