What kind of arb is he doing, buying traffic and sending to offers or buying clicks and sending to clicks?
With the latter it is still possible to make very good money this way, although not with Adwords as your source anymore but you also need a feed provider that pays top dollar, you can certainly make several thousand per day like this but 30k is exceptional if thats true.
Increasingly the problems for ppc affiliates and I have done arb for some 8 yrs are finding and keeping a top dollar feed and finding and keeping high volume and now quality source traffic. People who say its easy have no idea. It used to be easy, that would be more accurate.