The first M.2 horizontal space has connecting points on both sides, 3.0 or 4.0. The PCI-e slot has Steel Slot GEN 4 printed on it.
There's very little benefit going from SATA to NVMe; going from NVMe to slightly faster NVMe is going to show up in storage-specific benchmarks and that's about it.Perhaps that's the reason of the price.
Personally buying a mobo these days with out PCI4, high end, I think it's silly.
You can argue there's no performance gain on the GFX, but once you are talking about storage, they always benefit, even more going forward.
Thinking further on this, if a PCIe 4.0 x4 drive was fully consuming the bandwidth of PCIe 4.0 x4 and transferring it to a PCIe 3.0 16x GPU, it would only use PCIe 3 8x bandwidth, leaving 8x bandwidth for everything else, if compressed and decompressed by CPU vice graphics card then more. So in reality even if streaming from a SSD to GPU, it does not seem like it would directly slow down or exceed the bandwidth even with PCIe 3.0 16x. Maybe 3+ years or something. Now having two GPU's and halving the PCIe to 8x may become more of a factor, that is if you are using two GPUs.There's very little benefit going from SATA to NVMe; going from NVMe to slightly faster NVMe is going to show up in storage-specific benchmarks and that's about it.
PCIe 4.0 is more about keeping up with the Jones' right now; only very, very specific workloads will provide a measurable benefit.
That all said, no reason to skip it if it's there.