The Fiesta ST is a more specialty car. They don't have a lot of margin in the car to begin with and there's not a lot of them to sell so unless it's been sitting on the lot awhile they probably don't want to go down anymore. At least it's not like the Focus RS or specialty Mustangs where most are probably paying over sticker to buy them. I would have happily paid sticker price for my Fiesta ST, but I still searched for ways to get money off. $1k incentive from Ford Credit, $500 Ford college program, and $500 cash back from the mail. $2000 off was not a bad deal to me.
Shop around if any other dealers have Fiesta STs in stock, but it's not something many dealers do stock, and if they do it's one or two. I factory ordered mine because I wanted a specific set of options that no dealer in the entire US had in stock. $2800 off isn't a bad deal. If you like it on the test drive, you'll love it when you buy it and the purchase price won't be a big deal anymore once you're in and driving it.