Theres always somebody making something to a budget. I'm far from dismissive about it, lots of people just dont have the budget for Brembo/APs finest, they may only have the budget for (being polite) second tier products only once, what happens when you need to buy twice though.
You can get cheap castings from Eurac which then can get machined easily enough to be any size required, its the heat treatment thereafter that they dont get or the finishing process to make them black that debrittleises them. In fairness you wont notice enroute Asda, but its that 3rd lap at Oulton with your mate in front of you whos spent 1/2 as much and hes pulling away that is the real test for the second tier stuff often it doesnt end well
Mtec are the disc of choice at the moment, they get machined, blackened or plated and then sold. They start life as Mintex castings which are pretty much the most "cost effective" discs you can buy but nobody gives a toss because theyre cheap and black!
I machine castings but keep the feed speed down, coolant running and machine outside faces one day and inside faces the next. Im not under any real form of commercial pressure so can take my time luckily.
Subject to confirmation of a landed delivered price I'd be seriously considering these assemblies, this sort of stuff does need to be at a "tempting" price in my eyes however