IMO, yes. At the 1 cent per mile pay with miles valuation, that's $450 - or $125/hr. As a salary, that would be $260,000 a year, which seems quite generous. Or, looking at it differently, I'd usually cheerfully take a $400 voucher for a VDB that resulted in a 4 hour delay.

I don't know that this amount would be sufficient for me if I was delayed overnight and DL failed to provide hotel accommodations, for example. But for an average domestic delay of this length, I think it's pretty reasonable compensation.