I too struggled with the price of the SW Motech... but at the end, I am so glad I went with it. I even had to wait until the last minute to leave on my recent trip because it got delayed by a day...
I was able to have my meals/snacks, a shake, a thermos with hot soup, charge cables, spare battery pack, leatherman toolkit/knife, clean towel for cleaning helmet visor, two set of gloves, etc. handy at all times.
So glad I went with the EVO City size... it was perfect. I almost went with the smaller EVO Sport... that would had been too small for my needs.
I ended up spending US$294.90 for the bag and the locking ring. For me, it ended up being the right choice. Glad I got it.
SW-MOTECH EVO City QUICK-LOCK Tank Bag | 11-15L × 1
SW-MOTECH Type 306 EVO Tank Bag QUICK-LOCK Bottom Tank Ring × 1
Now to find out what the part number is for the relocation bracket from BMW for a GSA so that I can move the GPS higher. That is the only drawback with the tankbag... stock location for GPS is useless with the bag in place. That and the additional step of removing it during fuel stops. Removing the bag during fuel stops was not a big deal... not being able to see the GPS, was...