Definitly doable.
If he's got some automation going, wouldn't be surprised if it was gigsterrbot- he could easily blast his gig(s) over to 50+ acc's and use the mailer/harvester to generate more leads/ auto message customers, etc.
To the naysayers- VERY VERY doable to make 5-10k/mo with Fiverr, I've been doing it for months, the key is scaling / automation.
even if one he's just doing 200+ sales per day per account, (x) 50 accounts, 100 accounts, etc. = limitless$$