All posters on this thread and the cover in the OP are still active, so I will comment. First the price on
ebay dropped to just $3000. The listing's seller mentioned to me that it is a consignment item and thus, not the lister's price.
Yes it is a top piece and many of the known JQ5 covers are top pieces. However few folks will see enough JQ5 items in their collecting lifetime to agree or disagree. John Becker is spot on with his "quite a scare use" observation.
Parcel post and parcel post postage due stamps were never recalled. A postmaster could exchange PPPDs for credit in other values. So these dues either sat in an office for years waiting to be used or some offices were used to lower the distribution office stock count, especially if the office to which they were sent had a good demand for dues. So is 1927 late? Well it is towards the end. But remember the 75 cent PP Q11 remained on sale into 1929. Previously thought to be "only 1927." However I have not published the 1929 dating documents yet.
The lower 1, 2 and 5 cent PPPD values show up used 1927 and later, especially in the small offices which may have rared had a need for postage due use. All domestic post offices received both parcel post and parcel post due stamps for when the service began in 1913.
Now in my humble opinion, this is being offered about a grand or so over top price retail. North of $6250 is the highest open market auction price of which I am aware for a tied and dated JQ5 which sold 13 months ago:

