The sound has a very noticeable "t" sound in the middle of "vend-il", making it sound almost like "vend-t'il". I don't know if its supposed to be there, or if it's just bad computer speaking.
Yes, it is indeed supposed to be there. That is a liaison between two vowel sounds: en-il which would make difficult to say and difficult to understand.
That is why the final "d" moves to a "t" sound in front of a vowel.
How would I say "How much does he sell of it?"
"combien en vend-il ?" or "il en vend combien ?"
Given the distinctive "t" sound in "vend-il," why isn't "Combien le vendent-ils?" a valid answer?
the sound of "vendent-ils" is different VEN-DEU_TIL
I wrote 'how much he sells it for'? but lost a heart. Why???
it needs to be "how much does he sell it for?" You would be understood if you said it your way, but it's foreign -- no native would say it that way.
So how is "Combien le" = "How much for"?
"combien" = how much
"le" = it
"vend-il" = is he selling
we don't need a preposition in French to match "for"