A shelving system made to measure
A base unit plus add-ons: why the customer should see surcharges and how quantities are bounded cleanly.
A shelving system starts with a base unit and then grows. Two more shelves, a back panel, different feet. The customer does not think in total prices while doing this, they think in surcharges: what does this shelf cost me on top?
The configurator can do exactly that arithmetic. The setting Relative prices shows every line as a surcharge on the current selection instead of a full price. The correct total still appears underneath.
Prices shown as a surcharge on the current selection.
Quantity per line, not per cart
Three shelves are not three shelving systems. So the quantity sits on the individual line: Quantity selectable gives the customer a quantity box right on the row, and Preselected quantity decides what they start with.
Where a quantity should stay free but not arbitrary, that is what the set and its four rules are for, for instance “at least one piece, maximum the selected quantity (1 to x pieces)”. Upper and lower bounds are covered cleanly, and nobody puts forty shelves into an 80 cm unit.
Prices that apply only here
A shelf that costs 32 pounds on its own might be meant to cost 29 inside the system. That is what the Prices tab of the stream is for: you store an individual price per product there which is valid only within this stream. The catalogue price of the product stays untouched.
It is also the clean way to handle tiers that should apply only inside the set - the product keeps its own price and nobody has to create a second product.
Surcharges in percent
Some add-ons have no fixed price but depend on the value of the whole - a special finish, say, or measuring up on site. On the product itself you can therefore set Is Percentage Surcharge and store a percentage.
How the customer sees it is a second decision: as a Percentage Surcharge or as an Absolute Price. The first explains itself, the second is easier to compare.
Why surcharges sell better
One full price next to another forces the customer to do arithmetic. A surcharge answers the question they actually have. The total stays the same, the decision gets easier - and the summary underneath lists every line individually anyway.