accumulators ev question

[Pinocchio]

I have a friend who likes to do accumulators and i am trying to work out how the ev works with them, maybe someone can help me. From what I can work out doing an accumulator is the worst thing you can do with a bookie because if the bookie has miss priced an odd the ev you gain will be absorbed by the other prices being correctly priced in the accumulator, is this correct? (obv if the miss price on the one game is so extreme it can out weight the correctly priced other matches)

So if match A is priced incorrectly, but matches B, C and D are priced correctly than the ev you gain in match A is lost over the ev the bookie gains in B,C and D. Unless of course the bookie has made a major error in the price of game A.

So obv the better thing to do would be just bet on match A.

So would the only way to get a +ev accumulator would be by finding multiple prices which the bookie has got wrong and betting on them or finding one miss priced match which out weights the other correctly priced matches that you are betting on?

am i correct or completely missing the point?

maybe someone can help shed some light here...

ty