Ignition coils from RockAuto or eBay Motors?

I need to replace the ignition coils on my car. I can go to RockAuto and get a single ignition coil for about $40-60 a piece. How is eBay Motors selling a set of 4 ignition coils for the same car for only $50 total?

Different quality, or marked up on RockAuto? Which would be surprising since their prices are usually decent.

It’s the same code for both sites, UF540 for the coils.