What is the least expensive way to provide an 8-pin PCIe power connector when the power supply lacks this connector?

Using an adapter cable that connects two 4-pin Molex connectors to provide an 8-pin PCIe power connector is the least expensive solution. This approach allows you to utilize existing power supply connectors without the need for additional components or replacements. Adapters are generally affordable and available, making this option cost-effective while addressing the power requirements of the video card.

Replacing the power supply would be a more costly solution, as it involves purchasing a new unit that includes the necessary 8-pin PCIe connector. Removing the video card or selecting a different video card would not only be inconvenient but could also limit performance if the current card is more powerful than what is available as an alternative. Thus, using the adapter cable is the most economical choice while still enabling the use of the existing hardware setup.