prob around $800+ If it was just regular people bidding. My guess is a few stylists will try to grab it up for any one of the rappers that are trying to floss raf or something, and the price could end much higher.
spring always fits a little on the slim side because they don't allow for much layering. Generally speaking, the sizing is the same. I take a large in both spring and fall-weight jackets with a few exceptions here and there.
large will be too long. IMO other brands might be better with your build. I think you run the risk of swimming in a large. I am 6'2" ~175-180 and large is often too big and needs to be taken in.
Nepenthes is the father brand for all the clothing labels it owns. Eg, Needles, Nepenthes, south2west8, and they have a stake in barena (I think), mainland boots, owner operator, and some other brands.
For the Dayton, I love mine and...