You need some additional details. First, what exactly do they propose to do for that $900 USD? If that includes a tuning device like the Harley SEPST and about 5 hours dyno time, it may not be far off.
The days of a dealer being able to just download a $149 "performance" map directly to your bike are long gone. These days the only direct downloads they offer are street legal, thus not a "performance" map. Anything worthwhile will require a tuning device like the SEPST or TTS or whatever else is available in your country. Those devices don't come cheap.
Jerry
First, I'm a total Newbie when it comes to this, but as I understood it they would just download the "Original" US Map. To get these bikes to pass European legislation, they have a special Map minimizing CO2 etc..(like in California I guess??)
Since I already had installed Cat free Sebring mufflers, I specifically asked if it needed a Dyno tune and they said
that it was not needed. "But changing the Map would be a good idea"
They claimed that I would get 10% performance improvement, run cooler and more miles per gallon.