After news about Nokia N810 Wimax Edition being discontinued they're being sold on eBay for at least 250 USD, but doesn't seem to go beyond 300 USD. Second hand. Note these chips use 2.5 GHz spectrum; doesn't work everywhere; e.g. Europe uses mostly 3.5 GHz.

Be sure you know what you're buying and are aware of the differences with normal Nokia N810.

These I found approx 15 minutes ago:

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YMMV!