Unlike House or Condo, Co-op financing does not have mortgage tax, so price is irrelevant for lender related closing costs. If you do not pay any points typical lender closing cost would run $2000 - $2500. Could be even lower if you get any rebates, discounts from the lender based on promotions or your relations with the lender. Good Faith Estimate from your lender will have these costs listed which may vary very little at closing.
However, if you start adding your attorney fee, Co-op fees, flip taxes etc. it can ran into thousands. To get an accurate number you need to identify the Co-op first and ask your agent or attorney to get all the fees from the management. Remember, no two Co-op Corporations are the same even if they are next to each other and have same size, prices etc. Good luck!