Swissvignette is an independent commercial ordering service operated by a private company. It is not a government agency, not the Federal Office for Customs and Border Security (FOCBS/BAZG), and not affiliated with, endorsed by or acting on behalf of the Swiss Confederation or the official Via portal.
The Swiss motorway e-vignette can be purchased directly from the official portal at via.admin.ch for CHF 40.00. Customers who order through Swissvignette pay CHF 48.00 in total: the CHF 40.00 official charge plus an CHF 8.00 service fee, which is a commercial charge and not a public duty or tax.