At the risk of overestimating your financial condition
, $80 for the full set is a little expensive, but not bad for a 2-month trip. Keep in mind that it's more than just a street map, they include locations of hotels, campsites, shops, restaurants, bike shops, and sometimes elevations.
Even if you can't pony up for the maps, I highly recommend that you set aside funds for contingencies. It's inevitable that you will have unforseen expenses for a trip that long.
Besides, it'd probably cost you $50 to print out all of Steven's (probably copyright-violating, and certainly less informational and useful) version of the ACA maps on a home inkjet printer....
As best I can tell, your only other option here is to get a road atlas for $15-20 and figure out the route yourself.