Piper Jaffray’s Gene Munster has done some quick back-of-the-envelope calculations and concluded Apple is in it less for the money than for the strategic advantage it hopes to gain over Microsoft’s (MSFT) Windows 7, schedule to ship in October.

According to Munster, Apple is likely to sell 5 million copies of Mac OS X v10.6 in the remaining month of its fiscal fourth quarter for an average selling price of of $22 — less than $29 and more than the $9.95 Up-to-Date price Apple has offered customers who bought MacBook Pros after June 8.

At 60% gross margin, that comes out to $66 million, or $.05 per share — a bump that Munster believes has already been baked into the Street’s Q4 estimates.

So what’s really going on here, he asks rhetorically?

Despite the long list of improvements Apple is touting — it claims to have “refined” 90% of the more than 1,000 “projects” that make up the OS X — Munster describes Snow Leopard as “a minor upgrade … without many significant new features.”

In Munster’s view, Apple is using Snow Leopard as

“an opportunity to sell it at a lower price ($29 vs. $129 previously) and market the new OS as a selling point for the Mac platform over the Windows platform. In other words, Apple is promoting the Mac platform as a superior alternative to Windows in terms of newer technology, more frequently, for less money. The release of Snow Leopard is not about new features; rather, it is about keeping Mac users up to date with the latest technology vs. Windows XP and Vista users on antiquated technology.”

You can learn more about Snow Leopard — including what’s new, compatibility and tech specs — at Apple’s website here.