Forbes reports that surveys from sources as diverse as Indian retailers and AT&T managers confirmed that the Nokia Lumia 520 has been a surprise hit which is competing effective against Samsung and Chinese retailer’s low-end smartphones.

They report that interviews with three Indian retail chains indicate that the Lumia 520 is a substantial hit in August, competing effectively against the Samsung S Duos, while discussions with both T-Mobile and AT&T managers in New York, Chicago and Miami indicate that the $130 Lumia 521 for T-Mobile and the $100 Lumia 520 GoPhone for AT&T are now substantial hits in the contract-free category.

The handset offers a better screen and camera than other handsets in the same sub $160 price range, which may be driving sales, although they warn that Samsung will likely counter with similar handsets by Q4 2013.

The article notes that the Nokia Lumia 520 may be cannibalizing sales of Nokia’s high-end handsets, but that Nokia at present is aggressively pursuing volume over margins, as it seeks to build carrier relations while killing smaller rivals such as Blackberry and HTC, and guarding against the coming low-end iPhone, which at $400 will not be particularly low-end at all.

If this is indeed Nokia’s strategy they have indeed been executing it masterfully, and we hope the company is receiving enough support from Microsoft to ensure they remain viable while growing into the 10-20 million per quarter Lumia sales.

Do our readers think Windows Phone can win by hitting the low-end, or will it be a pyrrhic Symbian-like victory with large volume but low engagement in the end? Let us know below.