I've had employees at the Starbucks inside Barnes & Noble get annoyed at me for only ordering a tall drip coffee, since it drives down their average transaction

I've had employees at the Starbucks inside Barnes & Noble get annoyed at me for only ordering a tall drip coffee, since it drives down their average transaction size, this being the metric on which they're being judged. I tend to respond to upselling attempts with silence and a blank stare.