Pyrolysis has been identified as an ideal process to recycle mixed plastic waste (MPW). This study investigates the economics of a 40,000 t/y MPW pyrolysis process, called PlastPyro, located in Belgium, to an accuracy of +/- 15% i.e. "Definite Estimate". The process uses molten metal in a direct heat treatment process to pyrolyse the waste. An internal rate of return (IRR) of 20% strongly indicates that a 40,000 t/y PlastPyro plant is financially attractive for private investors. The capital expenditure (CAPEX) is estimated to be (sic)20.1 m or (sic)26.1 m if the cost of capital is included. The operating expenditures (OPEX) of the plant are estimated (sic)3.4 m per year. The sensitivity analysis shows six main variables having major impacts on the financial returns of a PlastPyro plant: (1) the addressable volume and quality of plastic waste, (2) the feedstock costs, (3) the capital and operating expenditures, (4) the revenues from the sale of the produced pyrolysis oil (P-oil), (5) the tipping fees and (6) the potential to co-locate a PlastPyro plant with a waste plastic sorting facility. For example, the 15-year low P-oil revenue price of (sic)210/t results in an IRR of 20%; but on the 6th of March 2020 the P-oil price may have achieved (sic)227/t, resulting in an IRR of 37%. The paper also shows that a reliable supply of MPW is available, and that reliable, accessible markets for the P-oil are available. Finally, cost estimates should state their accuracy and usually factorial cost estimates are not accurate enough to state the IRR.