Buying Airasia Flights Online vs. In-person

Just booked a flight online to Bangkok in early October for dirt cheap $228 round-trip for 2 people!
Lately, I’ve been curious about buying online vs. in-person as there is an official sales office in HCMC.
Ho Chi Minh City
Van Phong Ban Ve Tp Hcmc
254 De Tham, P.Pham Ngu Lao, District 1,
Ho Chi Minh City, Vietnam
[For more locations: http://www.airasia.com/vn/en/contactus.html]
The last time, I had to book in-person as my credit card was continually denied online. In-person was a straightforward and efficient experience, as I was equally straightforward and efficient with my requests.
This time around, after seeing the dirt-cheap promotion online, I wanted to inquire about the same exact flight itinerary in-person, to see how much of an up-charge it would be, if any.
There is indeed an up-charge: $290 for the same exact itinerary.
An up-charge, as unwanted as it is from a consumer standpoint, makes sense for Airasia’s side as they have to pay for the operational costs of the Sales Office.
Promotional fares are usually only valid on Airasia’s website. Booking online is the way to go.