The actual figures look like this for the March Quarter of 2009 and 2008:...
Laptops were appr. 65% of Mac unit sales. They declined 12% in sales volume and 2% in units.
Desktop sales declined 22% in volume and 4% in units. So Apple shifted dramatically towards cheaper desktops. This could indicate higher Mac mini and iMac sales versus less Mac Pros. That may have been a consequence of over pricing the Mac Pros.
...
Although Apple has done well over all it's computer business looks a bit shaken. The Mac Pro obviously is declining from a cash cow to cash out. Perhaps they will not bother with it in some years time.
Here's another source of data:
http://images.apple.com/pr/pdf/q309data_sum.pdf
What's particularly interesting about this one is that it breaks out the desktop segment both in units sold and revenue.
Thus, we can see that 849K desktops sold for $1,129M ... dividing, we get an average price per unit sold of ($1,129M/849K) = $1,329.80 per unit
Similarly, for laptops, ($2,200M/1,754K) = $1254.28/unit
Given that the iMac is in the ballpark of $1330, its influence on the average desktop price is relatively minor (think "short moment arm leverage"). However, since the Mac Pro is substantially more, its sales have to be balanced by sales of the less expensive mini...at very roughly at least a 1:3 ratio.
FWIW, I also took a quick look at the USA market vs other markets:
USA: $3,827M for 1147K units ... $3,336/unit*
Europe: $2,006M for 626K units ... $3,204/unit*
Japan: $416M for 108K units ...... $3,852/unit*
Retail: $1,496M for 492K units .... $3,041/unit*
* - Before reading too much into the above, do realize that the use of "unit price" is misleading because the data isn't broken out by product segment, and for whatever reason, Apple used a 'units' value of just Macs sold, even though the revenue is for including iPods/iPhones, iTunes, software, etc.
I'm not really sure if this is useful or not...it seems to more be a "Normalized Total Sales per Mac Unit Sold"...perhaps it provides some insight into the degree of cost-realism for the non-USA prices for Macs which have been a source of angst?
-hh