The Hindle Megaphone exhaust was under $600. Just a tad above $600 because I also bought the silencer. You'll need that! Is as loud as a Harley without it and sound great with it. I've had Two Brothers, Leo Vince, Akropovic. Save your money. Hindle sounds so much better.
I got the ECU flash from 2WheelDynoWorks... $239. Mail it out. They're fast with returns. You can have it flashed for a stock setup. They have multiple muffler/exhaust choices and make for any configuration, like if all you did was the exhaust they would open it up for you. Very happy with them. Cost me like $9 USPS Priority. Got there in two days came back on the fifth day.
If you're into luggage, do NOT get the factory Givi tail bag setup! It stresses the frame. This is a Hepco Becker C-Bow side case system. Multiple variety of bag options. Around $500 including those bags. 18 liter per side so low profile. I also have the factory touring screen and this picture doesn't show it but I have OES frame and front wheel sliders now.
The seat cushion is great. $30 on Amazon. Rode 3.5 hours and no butt soreness.