Question about ASUS GeForce ROG STRIX RTX 4090 OC Edition

Same price as in Germany and they have 20% VAT. But it's interesting with the 4090 OC from Gigabyte. It was available at Digitec for CHF 2450. . At Steg it costs 1999.90 CHF. How do you explain such a price difference? And what about the constantly changing availability?