We have received a voucher: 10X Cumulus points. "10x" in huge letters! At the checkout, we then regretted that we also had to read the small print "only redeemable from CHF 100".

that may well be a clever approach from your point of view. However, you should also consider how a customer who has been taken for a ride will react.

We will certainly not be shopping in Migros stores in the next few weeks and months - we have thrown away the voucher and will probably do the same with your next vouchers!