My app seems ready to get a \'real life\' test for an in-app purchase procedure on my device. However, I receive an \"The publisher cannot purchase this item\" error message in
I think the reason you got this result is because you ran the app in development environment.
To test in-app billing, you'll need to sign the app. See more info here and here.
This is indeed a nuisance and prolongs the dev cycle :(