Fee Engine.

Pricing logic held as data rather than code. Seven inputs, a package choice and a set of add-ons resolve into one defensible monthly fee — but the point is what sits underneath: every band, rate and multiplier is a row in an editable table, so loading a different rule set turns the same engine into a different calculator. Four are included here, and none of the four is written into the code.

Interface concept — not a live product. Nothing here can be signed up for or purchased; the figures are illustrative.