If you have more than 50 domains with namecheap you can request their bulk rates which gives you access to a special coupon code you use all the time. Saves a few bucks off their prices each time.
Don't think I could handle godaddies interface with that many domains. Just the amount of time looking at the upsells is a waste of life
The opposite of this is resell.biz. They go out of their way to never ever talk to anybody, and they're brits so they wouldn't know how to sell you an extra if they tried.