If you really think an Apple Store is only getting 10-15 plus, you're falling for the shortage hype
An Apple employee went on Macrumors and said his store, which is one of the biggest, got 20 total. Other reports are also backing that up saying that Apple stores are getting 3-4% of their stock in 6 Plus'. It's not exactly a jump to believe these figures when there were also the rumours of production issues and stock shortages virtually everywhere.
Not that it bothers me as my 6 Plus will be delivered by a nice UPS man shortly after I get back from the Apple Store with my fiancé's iPhone 6.