That's exactly what it is. And holy moly, let me get you up to speed with PMTA. (You know what, I need to make some bullins about this on the forum. I get so wrapped up on things I forget to push the information down sometimes)
PMTA is regulation that was passed by the FDA on August of last year. The enforcement period starts to happen this year. It goes into full force the end of next year. The gist of it is this, no new products can be sold on the market as of August 28th, 2016. Unless it was sold or available before that date. The real issue though is the e liquid. There is a list of tasks vendor most complete if they want to remain on the market.
1. Submit manufacture information to the FDA (Vapor Talk just passed this phase) as required. Failure to do so could result in fines and/or worse.
2. Ingredient submission ( the deadline was this month but, it's been pushed back another 6 months). e Liquid manufacturers must test and submit ingredients to the FDA by the next deadline. (Vapor Talk Black Label has certification right no the product page. We share the info publicly)
3. The big one... PMTA is extremly complicated but the gist of it is this: We must go through human trials among a full blown list of other requirements in order to continue selling eliquid and other hardware products beyond the end of 2018. As it stands, if using a consulting firm or similar the cost is roughly 800,000 - 1 million dollars PER SKU. (One flavor, 3 strengths would cost between 600,000 and 3 million dollars depending on a number of different factors) If you don't adhere to PMTA or cannot afford it, you must pull your products before the deadline. Additionally there are labeling requirements (for example no cartoon characters, no candy type images etc) This is were most of the dumping of products can been seen. In fact I've seen a ton of vendors selling pretty close to cost.
Right now a number of companies do not plan to go through PMTA. They are selling off their bulk and will close down. (They don't want to advertise this for fear you'll stop buying their brand and opt to use another because customers want consistency) Totally Wicked for example, have been around forever. Since we started. They are pulling out of the US market and will only operate in Europe. As it stands, if things don't change, 95+% of the vendors you shop with now will no longer be in business. Most of your favorite products will no longer be available if they aren't PMTA registered. (That's almost all of them) It's not.. looking good.
The attitude many of is "I mix my own stuff I'm not worried." That's true, but that doesn't mean it won't still have a huge effect on device and supplies. Most won't or don't mix their own products. I hate to think of how many people will continue using traditional tobacco after the vaping industry goes under in the US.
You can read more about PMTA here: https://www.vaportalk.com/everything-you-need-to-know-about-pmta/
So to answer, Yes vendors are selling of eliquids cheap and it's because of PMTA. (The VT store even has a sale on a number of eliquids under the deals page. Most at close to cost. No profit margins)