Macs are hugely popular in Italy among web developers. What I usually see is in offices, coworking spaces and conferences is a sea of glowing apples, my Linux laptop (I don't like the OSX GUI), very few Windows laptops, usually not the ones of developers. After all if you deploy on Linux, why develop on Windows? OSX is a good enough approximation.
I don't know what the average salary is (I bet it's not very high) but paying € 1500-2000 every two to three years for a tool you use to work is not out of question. My HP laptop is in that range but it will probably last more than the typical MBP (crossing fingers). However people resell their Macs quite easily when it's time to buy a new one.
Furthermore the computer is a cost so it lowers the taxable income. According to our fiscal laws if you lease something (somebody does that with computers) then it is completely a cost. If you buy it, you can deduce only 20% per year over 5 years. This doesn't apply to goods sold for less than € 500.
Small companies are starting to buy Macs as well. Probably the boss can't have the face to keep a Mac for him/herself and give Windows boxes to the developers :-)
Large companies tend to stick to Windows PCs but they are becoming less inflexible. Again, people used to iPhones started to think that they could work with Macs as well and so it's starting from the top there too.
Just another data point: here in Betahaus in Barcelona, I would say that 80% of people are using macs.
I think it's less about salary (except to some degree of course) and more about culture. When I do consulting for corporations I also only see Microsoft and HP or IBM, whereas even somewhat struggling freelance graphics designers or developers will have macs.
Outside US, it is a very small number.