This is because the city adjusted millage rates to compensate for the decrease in home values, but still collect enough to keep the government solvent. It's just another way the economic down turn is affecting everyone, even those whose livelihood has not been interrupted.
Your lender should be able to tell you how much will be contributed by the seller. Make sure the taxes are calculated on the current 09 bill, which may have been released in the last week.
Aaron is right.....plus, as we get closer to property taxes being due (usually in the Fall), lenders have to escrow enough money to pay a year's worth of taxes plus a cushion. At closing, the seller will pay his portion of the taxes which will appear as a credit to you. However, the lender will have to collect enough from you to pay the upcoming tax bill. In conclusion, the seller pays his portion to you, you pay the lender (prepaids/escrows) and the lender pays the tax bill. So, it may sound like a lot of money is being collected, but the seller is paying his part as well. The best person to question is your lender. They should be able to explain to you what they are collecting and why.