Updated with Bifinex as an example.

It is possible to earn 8% if you have account in Bifinex  and CEX.IO.

Lets take 1 ETH as an example. (in USD)
Bifinex buying $336
CEX.IO selling $376
Profit $40 (12% of your $336)

Minus
if using DBS 0% Remittance fees - 0% (depend on your bank remittance rate to wire transfer to Bifinex USA account)
Forex losses - 1.5%
BTC/ETH transmission fees from Bifinex to CEX.IO - 0.5%
Buying and selling fees at both exchanges 1%
CEX.IO Visa and Mastercard Withdrawal fees to your bank account 1.2% +usd $3.80

Net Profit 7.8% ($26)

The $3.80 is negligible if your investment is big amount.

If you use is on multiplier of 10 ETH, your profit will be $256.20 ($260-$3.80) for $3360 investment. 

I am in the midst of applying for Bifinex account since it is cheaper than Gemini.