To estimate the price of the 2018 Toyota Avanza I4 1.5L Commercial (Base) with 143500 km mileage, I considered the listed prices of similar cars. The closest match is a 2018 Toyota Avanza I4 1.5L Commercial (Base) with the same mileage listed for AED 28000. Other relevant listings include a 2019 Toyota Avanza 1.5L Commercial (Base) with 177000 km listed for AED 34500, and a 2020 Toyota Avanza 1.5L G with 146091 km listed for AED 49995. Given the age and mileage of the target car, I adjusted the price downwards from the 2019 and 2020 models. The 2018 model listed for AED 28000 is a strong indicator, but considering the average condition, I estimated a slightly lower price.