Think it may provide a profit but the main point of this is the better odds on BF SP, I had a 40/1 winner which paid 58/1 on Betfair. I have seen a huge difference in the past, I had an 80/1 win which went off at 250 on BF, that's 3 times the odds. Best I have seen is a 100/1 shot go off at 560/1 on BF.
I know but they are a bit hit and miss, last months shows one good win can tip the balance. With so many bets per winner it is a lot of outlay to bet EW and the place price on betfair is not always the best.