Cost depends on fluid type, required specification, testing documentation, and delivered logistics. Mineral oil is typically lowest cost, while ester and silicone fluids are higher due to materials and production. Inhibitor type, corrosive sulfur control, and oxidation stability requirements can raise price. Utilities may pay more for certified batches with full test reports, traceability, and long term supply commitments. Transport, drums versus bulk delivery, and site constraints also matter. For large projects, total cost includes filtration, degassing, filling labor, commissioning tests, and potential disposal of old oil.