No its not 70 a bag a few examples that work great
https://www.themillstores.com/collections/lawn-weed-disease-control/products/13-0-4-50-lsn-38-prodiamine
https://www.themillstores.com/collections/lawn-weed-disease-control/products/16-0-5-15-dimension-50-scu-pre-emergent-crabgrass-control-50-lb
Now do a soil test about 20$ send me results. Without having the soil correct first ( PH, CEC, N, P, K, Calcium and Organic matter) you are simply wasting $$.
This Fall Early Sept core aerate now when I say aerate I mean tear the crap out of it. 3 or 4 directions. Apply a good 3 way Turf Type Tall Fescue 250 lbs. per acre. At that time we will amend the soil for whatever it is lacking.
Yes in my years I have turned areas from complete trash to a nice stand of TF from Fall to following Spring and kept the Crab and weeds out.