I'm with the OP. He has done nothing but speak highly of these wheels until now. If it was a crash that caused it then he would be in the wrong to ask. However, the failure due to poor material selection warrants at least a hub at cost. From what he's saying he'll even pay shipping which is superb. I think he's being reasonable.

FWIW, I bought some wheels from another popular small business. I broke 3 spokes on the rear wheel. Each time, I replaced the spoke even though I have no experience. After the 4th, I email the owner again and explained my plight. I offered to send the wheel back to be rebuilt at my cost since I knew I had no clue what I was doing when I respoked the wheel. He declined my offer, and instead sent me ANOTHER wheel at no-cost AND let me keep the original. He had no reason to do so and definitely lost money on the deal. I'm currently in the market for some new carbon wheel and needless to say I know where I'm getting them from. That's customer service IMO.

OP I think at a minimum he should offer a hub at discount.
Rob