If you read interviews with the players you'll find several making mention of having their shoes specially designed for them. I gather it is usually reserved only for the upper eschelon players but you can feel pretty confident that what they're running around in isnt exactly what you'll buy in a store. The lower level players I dont imagine get the same kind of treatment. However, when I was playing football and the club was sponsored by one of the footwear brands those of us with fittings that weren't catered for by their standard shoe would have something made from scratch.
This is a little excerpt (didnt think you'd want the whole thing) from an interview with Ally Baker the young American player who was off the circuit due to a foot injury (she had the foot reconstructed).
" The modifications made to adidas tennis footwear is a service exclusive to adidas' Sports Marketing department, and is only available to adidas' contracted athletes. The cost of modifying a specific footwear style to meet the needs of a particular athlete's foot requirements can cost upwards of a few thousand dollars.
Ginger Tivey serves as one of adidas' Athlete Service Managers in the Sports Marketing department, and she worked directly with Ally. "The technical expertise that Ginger has is incredible," said adidas spokesperson Matt Martell. "She and our entire Athlete Service group can almost be called podiatrists, minus the medical degree. Ginger took molds of Ally's feet, conducted foot scans and various other foot-related tests. Once Ally's specific needs were identified, we went about modifying a shoe for her."