Dear BarbaraW
I would like to share my opinion also. Unfortunately, the amount that falls under taxation is not the one that exceeds CHF 500, but the entire value of the gift. In this case you will have to pay tax and AHV. Besides that, some of the AHV authorities value vouchers as cash and the whole vouchers amount can be also a subject of AHV, even if its is below CHF 500. I hope that my answer will be useful.
Good luck!