Answer:
I hear the "Hohner" brand melodicas are pretty nice. They're a German brand too, and you know what they say about German engineering.
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Ah, well. There are several competitors. Check out Melodicas dot com. Top models, according to performers, include:
Hammond 44 (2 models at $500-600)
Suzuki Pro37v2 ($300)
The wooden Mylotica ($300)
"Ordinary" melodicas come in at $100 or less, so you pay a premium for the best, and it may not be worth it if you're just a casual player.