U.S. retail sales of Apple Inc's Mac computers fell 16 percent in February on a unit basis, even as low-cost netbooks helped Windows-based PCs sales rise 22 percent, research group NPD said on Monday.

NPD figures are a closely watched measure for Apple sales, but they do not include data on direct sales from PC makers such as Hewlett-Packard Co and Dell Inc . The figures include sales from Apple stores, retailers such as Best Buy and e-commerce sites such as Amazon.com . Data from Wal-Mart is not included.

NPD analyst Steve Baker said Apple's high-priced products are proving to be a tougher sell as U.S. consumers struggle through a crippling recession.

I think the issue for them remains pricing in this kind of an environment, he said.

However, Baker noted that demand is difficult everywhere ... even though Apple unit volumes may be challenged right now, at the end of the day, they're a lot more likely to be profitable than other manufacturers.

Prices also came down in February. The average selling price on Mac laptops dropped around 7 percent to $1,512, NPD said. On the Windows side, netbooks' popularity was evident as the ASP on laptops tumbled 22 percent to $560.

Mac desktop units fell 36 percent in February, while Windows-based desktops dropped 10 percent.

Apple refreshed its line of desktops two weeks ago, and analysts expect sales to pick up in March.

Apple does not give mid-quarter updates on sales.

Shares of Cupertino, California-based Apple closed the regular session down 51 cents at $95.42.

(Reporting by Gabriel Madway; Editing by Bernard Orr)