Ha. I meant the rest of the equipment (USW-Aggregation, Unifi Pro Max 16, UNAS Pro, Unifi Express 7) was somewhere around half retail price.

I think I paid ~$15 for each X520-DA2 including postage.

I've started buying E810s even for 10G links. PCIe Gen4, lower power draw, RDMA support, generally backward-compatible with SFP+ DACs and transceivers, and relatively inexpensive. Not nearly as dirt-cheap as the X520s but not crazy expensive (last I looked, at least). As I gradually replace switches over the next few years I can start taking advantage of 25G.