$250 is actually pretty cheap for a Dorper.
$250 and up is about normal in our neck of the woods for Katahdins. Dorper are a bit more but they aren't as common around us. We looked at some Katahdins over the weekend not far from us but I'm trying not to put the cart before the sheep again.
I have seen another 0 added on !
If he's spending $75 a day now, how many head is he feeding? Since he's a neighbor and friend, why not ask him what he'd be thinking for a daily rate and adjust from there? For me, a lot would depend on how many head he'd be running back there...
Still don't know how many head... So just based on what you've said I'd be thinking $125-150 per week.