The “add on” is a deal tactic that involves a small opener, such as a low price, and then adding essential elements to the deal that make the deal itself useful for both parties (these may or may not be assumed as part of the deal for example, product without shipping, eye glasses without scratch guard, software without support, car without warranty). Prior dealings among the parties and industry standards may fill the gaps, but increasingly new commercial networks strip down what was part and the add-ons may swallow the deal. Why does this happen and why do we let it.
This is dynamic, as offerers (sellers) know the offeree (buyer) has no investment in the relationship until actual time is spent getting their mind around doing business. Sellers must focus on getting buyers; once that point is reached, relatively small add-ons are more acceptable. But it is getting agreement first that starts the “up-sell” moving. In other words, quoting a base price for the main item then add on necessary accessories e.g.: “Do you want fries with that…” “I’ll give you a ‘Basic’ mobile system but nothing works except email.” “If you want the car within five weeks we will place an ‘expedited delivery charge’ on it.” Time, place and manner of the deal drive cost.
We handle this tactic by brain and spine. Know what you want and ask for a quote on that in isolation as a buyer; sellers must communicate the cost drivers on why price and add-ons are linked. Kennedy suggests one of the methods we use at NSR: knowledge. Full disclosure at the outset of the pricing model prior to the delivery of a buying signal is what to look for.
 Once a seller sees a buying signal, the offer stops. Once a buyer sends one, the seller will stop the offer. Kennedy, Gavin. Essential Negotiation. Bloomberg Press, 2004: 33.