Give him time and find a great deal on a used cabinet, he may give in

Mine did! I found a cabinet bator for $200 and he gave in and let me get it. I don't think he ever imagined I'd fill it lol
That's the risk of it, getting stuck with a bunch of extra chicks. I advertise mine on pennswoods.net, craigslist, and Facebook pages. I try to make it to the tractor supply swaps too to sell mine. It happens though, getting sick with extra chicks. Those ones end up growing until they're big enough to butcher and go to the freezer. Unless they're pullets, then they usually can be sold fairly easy.