Doing it yourself costs only the government fee. Vietnam is $25 direct. The official portals work fine when your case is simple: one traveler, standard nationality, plenty of lead time.
A filing app earns its fee in three situations. First, tricky eligibility, like an Indian passport holder needing a Turkey e-visa with a qualifying Schengen visa. Second, group applications where one typo multiplies across six forms. Third, rejections: a second application means a second fee and a second wait, so catching errors upfront is cheap.
The old paper visa workflow meant embassy queues and paper forms. The e-visa moved the queue online but kept the rejection reasons. Whether you file yourself or use a service, the work is the same: correct documents, compliant photo, accurate form. The only question is who checks it. Sources: U.S. State Department VisaPack does the checking for $9.99 one-time per destination, then you file on the official portal yourself.