The first three are boxed city cancels, and as Peter4522 pointed out, were commonly used on Parcel Post packages. The third one may have been on a letter, given the period of use, but it is still possible it was on a parcel.
#4 is Seattle Washington, as you pointed out. In the PSS catalog, it appears to be type 225. The value is .10 for a well centered example, such as this one:
Both #5 and #6 are New York, N.Y. type L-16 HS with a value of .50 for the most common stamp with that precancel.
One of the problems with the precancel prices is that it doesn't take into account the value of the stamp, but only the precancel. Precancel collectors tend to rather strongly insist when buying precancels that the price in the catalog is what they should have to pay. Somewhere along the way to the point of selling, however, many tend to want to include the value of the stamp...go figure.
It's a long standing problem, which the PSS has started to alleviate somewhat with the issuance of the specialized catalogs for the earlier stamps where the stamp value has to be figured in.
Unfortunately, I do not have the catalog in hand which covers the later Washington-Franklin era stamps.
Perhaps someone else has that catalog handy and can chime in.