One add-on after the main choice, with a running total

How it works

Once a large price is settled, each small extra is judged against it and feels trivial, so add-ons offered after the main decision are accepted more readily. Offered one by one without a total, they quietly inflate the bill, and buyers who notice later return or dispute the order. A single optional add-on with a visible running total keeps the contrast benefit while keeping the final price predictable.

What the research says

• Car dealers settled the price of the car first and then added options one at a time; each seemed small next to the car, and the total grew well past the buyer's plan.

  Influence Ch.1, p.11

• Clothing buyers spent more on accessories bought after a suit than on the same accessories bought first.

  Influence Ch.1, p.10

Before you start

• An add-on with standalone value for most buyers of the main item

How to build it

E-commerce

After the main item goes into the cart, show one complementary item with its price, a one-line reason it fits, an equally prominent "No thanks" and the cart total updated live.

Web

On the confirmation step of a SaaS checkout, offer one relevant add-on (extra seats, priority support) as an unchecked line with the new total beside it.

B2B

Present optional services only after the core contract terms are agreed, one line each, with the contract total recalculated on the same page.

By product type

E-commerce / DTC

Purchase is the value event: one unchecked add-on at checkout is in season from M1.

What can go wrong

• Stacking several add-ons in a row until the total surprises the buyer.
• Pre-checked boxes: higher attach now, refunds and disputes later.
• Add-ons with no standalone value teach buyers to skip the step.

Pairs well with

• Pairs with in-t-cc-34: the first price shown already includes mandatory fees.
• Pairs with in-t-fn-06 on the main choice; the add-on comes only after it.