It's the Christmas spike. Normal prices can be found 1,200-1,500 round trip if not in peak season and enough advance. Christmas/NYE prices are absolutely absurd.
I can't speak directly to that re: the DTV, but we've heard similar for Non-O. They've stopped granting new follower visas to kids (even babies/toddlers/etc) at consulates (at least all that we've seen), and having the children go in on Tourist visas--presumably to overstay. Seems like a really sketchy practice to me, but seems that's the direction it's going.
I'm guessing they've maybe had the pattern for 6 years, but you wouldn't be able to go 6 years without paying. It gets flagged on the extension (max of 1 year).
But I've wondered if you could possibly just not do 90-day reports and pay the 2k at extension time with no issues. 🤔
VietJet is even worse--7kg carry-on. Last time I flee I didn't expect that to be tightly enforced as that's just my laptop and bag together weigh nearly that (and we had excess checked baggage space).
Sure enough, they checked and were going to make me pull and check my carry-on, until I slid out my laptop and showed them, then weighed again. The lady said "okay, just carry that separately". 🤦