Question about Synology Ds918+

Why has this product become more expensive since I bought it from digitec in January 2019 for CHF 599? And the current price of 654.- is advertised as "reduced" instead of the "regular" 733.-. Other suppliers haven't increased their prices either. https://www.toppreise.ch/preisvergleich/NAS-Systeme/SYNOLOGY-DS918-ohne-Festplatte-p505466