By Slash Lane

Published: 10:00 AM EST

Investment bank Piper Jaffray on Friday called out Wall Street for not fully recognizing the impact of price cuts on Apple's new Mac notebook lines introduced this week, saying the move will in all likelihood boost the company's quarterly Mac growth to respectable rates in line with his model.

Although market research firm NPD won't release data on Mac unit sales for the month of May until Monday, analyst Gene Munster told clients in a research note that he expects sales will be down on a year-over-year basis by approximately 2 - 5% for the month.

That said, he added Apple may remain in position to meet his June quarter estimate of a 10% year-over-year decline in Mac unit growth for the three-month period even if May sales theoretically fell by as much as 28%. (The Street is currently anticipating an 8% yearly decline.)

"This assumes that the month of June is up 5% year-over-year. We believe June could be up 5% year-over-year due to the new Mac portables with reduced pricing that shipped on June 8th," he wrote. "In the month of March new desktops drove NPD units up 3% year-over-year; we believe the changes made in June are more significant, and will likely drive higher growth of about 5%."

Munster, who maintained his Buy rating and $180 price target on the Mac maker, also expects NPD data to indicate that iPod unit sales tracked down 5-10% for the month of May, which would be in-line with his June quarter unit estimate of a 7% growth decline.

"The big picture" is that "[we] believe the Street is underestimating the positive impact of Mac price cuts announced on June 8th," he wrote. "As such, we expect the June quarter to mark the trough for Mac unit growth rates through the balance of CY09 and we believe the Street is not fully appreciating the positive impact of these price cuts on unit growth."