This kind of discussion always makes me think of Bob Pease's comment that he uses his computer for data entry, record keeping, and writing articles and technical papers, so he required a computer that would be able to handle his work speed, which was on the order of 0.00000001 GHz. People who create large and highly detailed artworks, on the other hand, really need that speed.
Your guy is a speed guy. What does he use the computer for?
Is he looking at actual usage requirements, or only how fast can it be?
Does he want a really fast LAN, faster than his internet?
What is he using to measure the speed?
Is he getting internet speed in any way comparable to his network speed?
Did he connect to a hub instead of a switch? (probably probably not, but just covering bases)
Forgetting that the prices are Australian, does this help at all?
You say
The Netgear piece's manual states that it passes 100 Mbps down with CAT5 and 1000 Mbps down with CAT5e.
This is a bit suspect. To make it blatantly obvious, if one were to connect "the Netgear piece" with a foot long piece of CAT5 and a foot long piece of CAT5e, would these differences appear?
And of course..I was a bout to quote two hundred words from
[Link: lifewire.com], but let me leave it at this:
How Fast Is Gigabit Ethernet in Practice?
Because of factors like network protocol overhead and re-transmissions due to collisions or other transient failures, devices cannot actually transfer useful message data at the full 1 Gbps (125 MBps) rate.
There are two important things here. One is the bare facts, the other is the reminder that 1 GBps = 125 MBps.
