Apple products are always ahead of other similar products. Therefore, we can venture to estimate.😀
Back during the PPC era, that would have been a valid statement. But not these days, especially with graphics cards (only one professional card - Quadro 4800, and the other offerings are late compared to the PC release dates - so long in fact, newer products are soon released by the time the Apple variants tend to ship).
But if you look at the recent history, they're behind over-all as well. Just look at graphics cards in further detail (not just old, but lack features such as HDMI or full size DisplayPort), and lack of BluRay for example. Other vendors have had these out for some time now.
And then you can get into such details as access to firmware (which Apple used to do pre Intel, but no longer), and lack of value added features that are included on other boards such as eSATA, additional SATA ports, SAS ports, built-in RAID (via a hardware controller chip), or more PCIe slots). And this can/does apply to some workstation boards, not just those meant for high end desktops, such as gaming rigs.
Mackilroy, you may be right, but it seemed that it was tech based, not cost to me as well.