Is arbitrage possible or is it a case of if it seems too good to be true .....
It is certainly possible but you should know which trading pairs are good for this purpose and which are not
For example, in the past (around 3-4 years ago) I had been actively using arbitrage with BTC:DOGE pair on 4 exchanges. My best result was earning 0.7 BTC with just one iteration (just in case, back then Bitcoin wasn't that expensive), and it all came through manual trading. Not so long ago I was using this technique with Litecoin earning a few percentages on a trade. But that required a specialized trading bot as it is nearly impossible to catch sudden price changes in the "manual" mode (which is basically what today's arbitrage comes down to)