Faithful retranscription of my conversation yesterday late at night at my local combini:

Bored Teenage Combini Employee: Hello and how may I help you?

Dave: I’d like stamps. Do you sell stamps?

B.T.C.E.: We sure do.

Dave: Brilliant. In that case could I get for 90 yen worth of stamp?

B.T.C.E.: Unfortunately we do not have that.

Dave: But I thought you just said you sold stamps…?

B.T.C.E.: That we do!

Dave: Then how come you don’t have any?

B.T.C.E.: Oh, but we do have stamps.

Dave: Then why can’t I get my 90 yen stamp.

B.T.C.E.: We only carry ¥50, ¥80 and ¥10 stamps. Sorry.

Dave: facepalms.