personally I don't have so few big accounts that loosing one will hurt. up until this post my comments have been from the view point of if I hypothetically had a 20k account.
I'm solo and currently do only residential properties. 90% of my business is mow, trim, edge, blow and go. if any one of them wanted me to drop my price 5%, they'd be saying bye bye to me for sure. I don't dicker on my prices for anybody or anything.
but yes it's an excellent point to not put all your eggs in one or a few baskets.