It varies by location...but in some areas the VT sells well in other it doesn't. IME I have found that more people are looking for a cool looking Betta for a pet with no intention to show and haven't a clue about standard-they either like the looks of the Betta or don't.....
The VT is the grandfather of all the tail type and why it is called a mutt I don't understand and with the standard PK being the short fin version of the VT....These are what started the Betta craze and with years of selective breeding they helped to create the other tail types......
The Betta either meets standards or it doesn't-the biggest difference with breeding pet shop and Betta from a breeders is knowing genetic history and even still...sometimes you don't get genetic history from a breeder-not all breeder keep good records and even with known genetic history you can have some surprises. When working with mystery genetic you never know what you will get and sometimes it can take several generation to reach your goals....This is dependent on what your goals are too.....
Some argue that it cost the same to spawn, rear pet shop or what they view a poor quality Betta as it does to rear high quality and while that is true, whos to say one is better quality than the other or more worthy...Just because one cost more doesn't make it better-I have seen many Betta on aquabid with high price tag that are of poor quality or better term...didn't meet IBC standards. You will not find the perfect Betta-they all have some faults be it minor, major or disqualifying....
You will always have the "Nay sayer" when it come to pet shop and VT Betta breeding. Usually they are IBC oriented or a breeder themselves and would rather you buy from them-
nothing wrong with that either by the way. We have some fine breeder on this site. But whos to say they are right and you are wrong in your choice of a starting pair to spawn.
Since the IBC doesn't have a standard for the VT-they are frowned upon. My understanding of why the VT doesn't have IBC standard is due to the VT being difficult to fix the fin to meet a standards-but I am not 100% sure on that-
Since the other tail types have become more popular the Betta that started the Betta craze to begin with has been set on the back shelf...so-to-speak....Had it not been for the long fin VT we wouldn't have the tail types we have today....The Veiltail was the start of it all.....
The biggest problem with any tail type with or without known genetic history is...What to do with the offspring......IMO-you should be breeding for quality not quantity anyway and should cull hard regardless of the breeders you start with.
IMO-nothing wrong with starting with pet shop Betta, VT or even mixing tail types-But you need a plan for what you are going to do with the offspring and a goal to work towards-even if its to gain experience to find out if this is something you want to get more serious about.