Keep in mind price isn’t the only consideration. The cheapest panels usually don’t fit as well, requiring more work to get the installation done.
For the quarters it really depends on the amount of repair needed, if you just need to patch the lower sections you can buy the rear lower patches, or one of the quarter skins and just use the parts you need. But at some point installing the whole OE style quarter becomes less work, so if you save a few hundred bucks but then spend several extra days welding and doing body work it may not be worth it.