Remember Switzerland is a multilingual country (4 official languages are recognised), so the internationally accepted CHF currency code doesn't work for all of them.

In fact, nearly two-thirds of the population are German speaking and the amount as far as they are concerned would be in Schweizer Franken. Hence S.Fr.

And Biel is just inside the German-speaking region:

though you'll also see from that map that Bern is officially a bi-lingual canton.

As to why it would be that much cheaper, well I'm sure some of it would be accounted for by no export or customs duties. Whether that's enough to cover all that difference or if some of it is just the Swiss taking an extra cut from the US, I'm not sure! A bit of both, I'd wager.