This is all pretax income since it's deductible, so you should be multiplying it by your (1 - marginal tax rate) to get the real equivalent price. Assuming he probably makes more than $180k AUS ($127k USD), his rate is probably at %45, so the 'real' price for this is $5720.
I am an artist living close to the poverty line, I know absolutely nothing about how “business deductions” work. He still had ~$10.4k of cash or credit on hand all at once to turn into this pile of hardware, right? That sounds pretty real to me.
He mostly linked to manufacturer pages, I did not feel like spending the time to see if there were better deals out there. Feel free to spend an hour or so on that if you want to.
Also the prices your looking up are pretty inflated. I did a very lazy amazon search for the CRG90 for example and I got ~$1500 right off the bat: https://www.amazon.com/gp/offer-listing/B07L9HCJ2V/ref=sr_1_...