Yes, Vietnamese registrar are much more expensive. From my experience, my understanding is that you need to be legally register and show a proof of registration of your business or NGO or what ever you are in order to get a .vn domain.
it's not like other TLD such .com, .net or .org which you can register on line in 2 minutes.
As for sites outside of Vietnam selling .vn TLDs they charge much higher as they are not on site and i guess they charge for all the time and paperwork they will have to do from abroad. And i am pretty sure the .vn domain business is taking care by the government. Don't forget, everything related to publishing information is manage by the authorities.
But one thing for sure is that for other domains than .vn don't go with local companies. they charge more for nothing, and they often don't give access to your control panel.
They basically register it as an individual and charge you much more.
I actually check ICANN registrar list and could not find FPT or others who claim to be ICANN accredited.
i hope that helps
cheers
