Exchange rate is lower, last time I looked it was about 1 baht/$ lower than googles exchange rate. There's also a 1% fee to withdraw money from the account, and if I remember correctly, you can't withdraw USD, you have to convert it.
VFS global is a government contractor. The Thai government chose them last year to process e-extensions. VFS global also does visa and passport work for the British government and India.
The 1900 baht fee is the governments fee. If you use the online service through VFS global, there's an additional fee.