I was wondering what new information I could give apart from what is already known, as the thread starter has already searched the Zurich region post doc salaries, and has been a post doc for 2 years.
In short, post doc gross salaries vary vastly. After considering family status-tax rate, care allowance etc, the difference can be spectacular. E.g. the take home of a post doc in ETH at 60% position who is single, can be
less than half the take home of someone at 100% position and with kids, in the same department. I am not even talking of industry sponsored positions, but the regular positions.
Annual increment of some 4% exists if you stay in the same institution.
On balance it is more common for people to move at increasing pay. I do know of people who were at 100% at EPFL for 2 years (which means he had one increment), and then moved to ETH at 60% position (at entry level grade within the post doc band).
Given such a wide disparity in salaries, I don't see the point in speculating what will be offered at Bern. My suggestion: Just ask them

. And if possible, negotaite a fair deal; I am sure with 2 years of exp, you know they have a fair amount of discretion. The previous posts give a good idea of the range.
All the best!