hmm yeah i see,
even if one were to just put a shit load of btc and usd into both accounts.. say like 30k worth of bitcoins and usd into both exchanges (120k value total)... eventually one account will be full of USD and one will be full of BTC.
you still need to withdraw half of the USD and send it to the other exchange, and vice versa with the bitcoin account...
no matter what u cant avoid those transaction fees.
unless...
yeah u need a lot of money but,
https://www.cointhink.com/arbitrage/btcusd
as u can see some of the top volume exchanges do cross...
so you can just arbitrage the accounts back and forth whenever the arbitrage between the two exchanges flips. of course much easier said than done...
that being said, a lot of ppl mention the wait times for confirming your order... which is unacceptable in the world of arbitrage... it needs to be near instantaneous confirmation.
if anyone is into math or programming or whatever
http://www.fem.uniag.sk/mefi/pdf/arbitraz.pdf
this is pretty good for the formulas needed to calculate profit.