How to build it, and what each way costs

Compare the ways one construct can actually be made — order it whole as a sequence-verified clonal gene, buy only the pieces you cannot amplify, PCR everything out of plasmids you already have, edit one plasmid by mutagenesis, or anneal oligos for a short piece — each costed off a published US list price with the page and the date it was read. It first works out which stretches of the target occur in the templates you give it (either strand, through a circular origin), since the stretch you already hold is the one you do not have to buy. Costs cover ORDERED items only: synthesis, oligos and sequencing. Enzymes, master mixes and competent cells are not costed, because no vendor publishes a price for them without an account and they are much the same whichever route you take. Nothing here predicts whether a reaction will work; each route states its own failure mode instead.