Very nice .mobi for development. Maybe mid xx at most to reseller, but could fetch a premium rate to the right end user. IMO I could see a major bank paying xx'xxx for this domain. I would develop it into a mobile site showing the location of ATMs, or maybe design a script which shows the closest ATM using a mobile GPS? Once the site receives good traffic, approach some large banks and you could fetch a premium price. I personally would not sell this domain without development