I don't find him manipulative, or a bastard. It's a business negotiation, and he's opened the negotiations at an amount he probably doesn't expect you to accept. Very often, this is how business is done in his world, and it's not an expression of him not appreciating you properly. Rather than see it as a personal insult, you can find an amount you'll happily accept, and charmingly hold out for it. Would ?1200 be acceptable? If so, tell him, and let him go away and think about it. If he won't offer an amount you'll be happy with, then tell him you'd rather keep your (business) relationship on the familiar footing.
I have so often got in a huff over some imagined slight and told a punter to sod off, only to afterwards regret it and wish I'd handled it better and not shot myself in the foot. It'll just mean some other WG will earn the money, and you've lost a punter.