Alcatel C1 was $9.99 (att prepaid; earlier this month), runs 4.4.2

ZTE Whirl 2 is $9-19 and runs 4.3

Moto G is $29 (<!!!, as of last week - probably sold out by now, but max 2 per person on bestbuy.com; boost mobile moto g's standard price is $39 either way though: this is probably the best price:performance ratio in terms of not being a complete POS)

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I pick up a few oddball phones for android testing/development.

These are locked to a specific carrier every time I checked - they are subsidized. I've never seen an unlocked Android for less then $39=~$40 (But I don't look often, so I might have missed some)

Probably. I don't activate these, I just use them to test my apps on small screens and incredibly shitty or old OS or other stuff.

Some of these have like.. 300x480 screens or something equally ridiculous, which is a nice way to test for "see how bad your app can get". It helps that they are all "legitimate" phones, i.e., have the full Play Store and ecosystem (supporting push, google accounts, etc).

Hmmm, can't seem to find any links for the prices you mentioned. Citations?

Alcatel C1 is over now, it was $9.99 (also https://www.att.com/deviceunlock eligible, IIRC) - bestbuy

ZTE Whirl 2 is $10 still (active, in store only) - http://www.familydollar.com/pages/hotitems.aspx

Moto G is over now, it was $29 on bestbuy, carrier locked to your choice of Boost, Verizon, or a few others. Not rootable

The Alcatel C1 is MT6572-based so should be easily rootable and unlockable.

True some are carrier locked but unlock code can be purchased for cheap (for some phones).

Plus there are lots of used phones smartphones for cheap.