Flying to Vietnam from India ----
City of Departure: Bhubaneswar
City of Arrival: Ho Chi Minh City
Transit via: Kuala Lumpur (You don't need a Malaysian visa if you book fly-thru tickets with AirAsia.)
Roundtrip Cost: 10500 INR ( I purchased 20kg baggage allowance for an additional 2200 INR. Also, purchase the in-flight meals here cause they're much cheaper when you pre-book them.)
Visa for Vietnam: Total cost 42 USD.
There are 2 steps as follows.
Step 1: Apply for an e-application choosing your intended duration of stay (1 month, 3 month or 6 months) and if you want a single entry or multiple entry visas. It's a simple procedure and the approval letter will be sent to your email ID within 2 days. The cost is about 17 USD for a single entry visa.
The visa letter is a complete invasion of privacy as it's a weird letter with 15 odd names stating their intended date of entry and exit from Vietnam and from which country they belong to.
Also, I recommend waiting until maybe 2 weeks before your departure to apply for this. Because I'd applied months ago and my AirAsia flight got preponed at the last minute and I'd to re-apply for the visa and lost out on 17 USD unnecessarily.
Step 2: You will get a visa on arrival at the airport in Vietnam after you pay a stamping fee of 25 USD. You have to pay in cash, so keep it ready.