For proper tax procedures you will need to bring a tax back voucher (in Switzerland you won't get much, though), then you have to get that stamped by border police. At the other side of the border checkpoint you will need to pay taxes for importing. Don't try to sneak past that point, because there is often video surveillance. In addition there are frequent controls at all parking spaces and fuel stations in the vicinity of the border (Zollgrenzbezirk). It only makes sense to buy across border in case the combination of price difference and customs procedures make it profitable. As I have stated before, buying professional gear in Germany is currently better for me, while buying cheaper lenses/gear (e.g. CF cards) is not.