Couture hats start selling at £750, but those who covet a more elaborate sculpture spend as much as £4,000 ($6,200). People start booking appointments as early as January when Royal Ascot's ticket office opens.
"The client first shows me their outfit, but I also look at face-shape, colour, complexion, and personality. Next, I'll design a hat that complements all these aspects, but also come up with other design options to wow the client," Tracy Rose told CNBC, who added that after measurements and fabrics are discussed, there'll be at least one fitting, with the overall process taking between 3-6 weeks.
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Currently, luxury department store Harrods is selling high-end hats from designers such as Phillip Treacy and Rachel Trevor-Morgan, for prices ranging from to £599 to £1,050.
Sellers even work from abroad, with MAGGIE MAE DESIGNS® in Cape Cod, MA, selling created-to-order couture hats online from $498 to "well over $1,200" according to Sally Faith Steinmann, the owner and designer.
Equine sporting events account for 50 percent of the company's total hat production, with spring being the busiest for designing.
"I love creating hats for Royal Ascot because of the rich heritage and history of hats and horse racing associated with this more than 300 year-old racing tradition," Steinmann told CNBC.