It's like a $30-40 difference. Since the 4830 just came out, it's not as common to see it heavily discounted/rebated, so typically around $100. If you can find a 4850 in the discounted neighborhood of $120, it's a steal at that price.
Currently the lowest price for the 4850 on NewEgg is $140 with discount/rebate for the asus and sapphire.
Lowest price for 4830 is $110 w/ rebate for PowerColor
4670 goes as low as $70 w/ rebate for the Asus
Pretty broad range, but if you overlook the 4670, which I haven't seen any benchmarks for, you're not paying a huge premium for the 4850 over the 4830.
$20 difference wouldn't be an issue. $30 difference is really up to buyer want/need.







