The $500 came from the new chips, plus the motherboard Apple is using is much higher spec than the SuperMicro.
It's got 8 full length PCIe slots, and two of those are the MPX slots so it's effectively 10 if you use MPX cards. It has dual 10gb NICs, and two TB3 ports.
It's got 8 full length PCIe slots, and two of those are the MPX slots so it's effectively 10 if you use MPX cards. It has dual 10gb NICs, and two TB3 ports.