A young guy starts his first job a general store in a country town. His new boss tells him about up-selling, then a customer walks in and the boss says "Watch me, I'll demonstrate"

Customer: I'd like a bag of lawn seed please

Boss: Certainly Sir, 1 packet of Lawn Seed and a bag of fertilizer

Customer:  Why do I need fertilizer?

Boss: After you've sown the seeds you'll need to fertilize the area to promote growth.

Customer: OK

Boss: Right then, 1 packet of Lawn Seed, a bag of fertilizer and a watering can

Customer: Why do I need a watering can?

Boss: Newly planted lawn seed needs to be gently watered, if you use a hose you'll just wash the seeds away.

Customer: OK

Boss: Right then, 1 packet of Lawn Seed, a bag of fertilizer, a watering can and a lawn mower.

Customer: Why do I need a lawn mower?

Boss: As your new lawn grows you'll need to trim it every few weeks to maintain it.

Customer: OK that will be great!.

So the Boss finalizes the order and the customer leaves thankful of the great advice. He then says to the young guy, "See it's all about up selling,  you try with the next customer".

With that another customer comes into the store, he walks up to the counter and very quietly asks for a packet of Tampons.

Young Guy: Certainly Sir, 1 packet of Tampons and a lawn mower.

Customer: WTF, Why do I need a Lawn Mower????

Young Guy:  Seeing that your weekend's stuffed, you might as well mow the lawn!.