"Moe Sham" is a maid-themed hair stylist shop towards the north-west corner of Akihabara, a little past Candy Fruit Optical. I haven't gone inside, but it is fairly well documented on youtube, including a video that the maids released themselves. The website carries an event calendar, a price list, photos of the maids and a blog by the maids.
By western standards, it's pricey, at 2,000 yen for a shampoo ($20) or 5,000 yen for a man's haircut, but by Japanese standards this is probably about average (some salons charge 8,000 yen for a men's stylist). Keep in mind, too, that you're being attended to by maids! ;-)