Data point: ZRH-BKK-ZRH Z fare $2400. Flew outbound in March, but return was cancelled, had to buy new ticket on KLM to get back home.
Ticket booked through Expedia. Expedia made multiple attempts to contact Swiss about refund with no reply.
In August disputed half of the charge with Amex (DL Skymiles). I received $1200 credit immediately and now I see that dispute status changed to CLOSED, so I assume everything went well. Probably Swiss did not bother to reply to charge back .