So what if you buy an used lens from Swiss citizen? Are you supposed to pay VAT on that too?
What if you live in Switzerland and go on holiday in your home country? Are you supposed to pay custom fees on all your goods - that you of course bought where you live?
I can tell you what the procedure is. I have exported around 40 camera items to Germany, Netherlands and Greece in the past 12 month.
Anything you bring from Switzerland over the border into Germany, that surpasses the free value of 300 Euro need to be declared and VAT will apply (21%). The chance to get searched is minimal and if you don't carry any box with you and you put camera and lenses in the bag, this should be no issue at all.
Anything sent by mail that surpasses 50 Euro, VAT applies. In this case it is like playing Euro Millions. Some of my sendings were taxed and others not. Not the value made the change, thats for sure. The Sony Alpha 900 i sent to Cologne was never taxed. Passed directly to recipient. On the other hand I sent an Acra Swiss Plate to Germany and the german customs asked for VAT

The most improtant thing for German customs is that a proforma invoice is being attached outside of the package and the amount looks credible.
Thats it.
digitec.ch, heiniger ag and brack are good shops I can recommend.