Every price on this site is made of three lines, and the quote tool shows all three before you pay. None of them are padded, and none of them are hidden.
Material
Your part is weighed before it exists. The quote tool reads the volume of the model, works out how much of it is solid at the infill you chose, and multiplies by the density of the material. That gives grams, and grams times the per-gram rate for the material gives the first line.
Supports add a little, so the estimate includes an allowance. If the real figure after slicing is lower, the difference is refunded.
Printer time
The second line is hours on the printer at a flat rate. The estimate comes from how much plastic has to be put down and how fast the printer can put it down at the layer height you picked. Fine layers take longer. Tall parts take longer than wide ones because every layer change costs a moment.
Print settings used
Setup and file check
Three pounds. It covers opening your file, checking it in the slicer, setting the plate up and starting the job. It's the same whether you order one part or forty, which is one reason the price per part drops with quantity.
If the confirmed price after slicing is higher than the estimate, you're asked first. It's never charged without a yes.
What moves the price
Infill moves material. Layer height moves time. Material moves both, because some filaments print slower. Quantity moves everything, because the setup is shared and the printer runs more efficiently with a full plate.