bulk powder of shady grade from china might be alot cheaper then sintered tiles with specifications.
You can just make the cones bigger I think with little consequence so long you stay in certain frequency bands. Ferrite is mainly designed for inductors I think, so using it as a general 'i dont want reflections here' might allow for loose specifications.
With a ferrite tile they probobly sinter it and measure it and there are rejects due to process errors, inspection costs of initial powder and finished product, chipped stock that does not sinter properly, bad distributions of ferrite, improper geometries, mold maintence costs, sintering cost, furnace upkeep costs, factory calibration costs, stock maintenance cost (they are kind of difficult to store as they are heavy and fragile) skilled ferrite technician costs, shipping cost and then multiply cost by 4-10 for company profit depending on how niche it is. If they sell a tile for 5$ that means probably ~1$ of raw material went into it (or maybe much less).
since we are spraying it in a garage with ceiling material some liberties might be allowed to reduce costs, I kind of imagine it showing up in a giant 'chemical bag' like you get seed, rocks or industrial chemicals in, the one that you basically lift into the air and cut it on the bottom made of nylon.
With some kind of home made antenna tester I think what you are looking for is a way to detect which signals are bogies so you can ignore them in your head rather then try to get some kind of universal 'every joe on the street will know what this graph means' thing going on, especially when you are using it as a calibration/reference standard against a hill you found outdoors.
I don't want to stifle discussion of high end solutions but I don't want to see this degrade to cave technology because someone found some price of some manufacturers product, we have yet anyone with experience in the ferrite tile or anechonic pyramid/cone manufacturing field to tell us how sane or insane we are, but I have yet to find some kind of encouraging ferrite price war between two companies undercutting so it might be a stagnant niche.
To put prospective on it, he is getting 3000lb of tiles for 50k, meaning that the material finished inspected certified all that jazz is 16$ a pound, vs the 160$ a pound of raw unworked material someone found.
That means 3000 units get you a bulk discount of 90% of finished product. Thats kind of strange imo. I figure that 150$ a pound is worth something like <<20$ a pound, 90% for 10,000 units is a bit of a steep curve for bulk buying IMO, 30-50% price would be a good deal @10,000, and thats finished product. I would like to know more about how those factories run so I can understand the cost reduction with volume that occurs. It makes sense to me because you get 16$ a pound finished for 10,000 units at say 50% discount, so a single unit might cost like 32-40 dollars, and thats a damn finished product, with 4x markup on materials say, so thats 8-10$ a single pound, but they wanna charge 150. Even if you multiply it by a really bad 400% small guy bullying/inconvenience cost, you still get like what, 40$ a pound?
150 a pound is cringe, even with a 400% bullying small customers cost. I bet you can get chinese stuff at 5$ (hell or less) a pound for 50 pounds.
The powder screening process is probobly throwing it into a ball mill and paying someone with a particle mask 12.50-15 an hour to beat a seive with a rug beater to get 'engineering particle grades' and some tech 17-22$ an hour to look at a sample of a 100kg bag of it under a microscope (they probobly get the raw materials from china too, off alibaba)
I think people are just willing to pay because the people that are typically interested in ferrite tiles would be rather well educated RF engineers that are all neat, understand mathematics, nice clean temperature controlled office etc. I don't see them wanting to fuck around with giant bags of dust and 'kiln conditions' that bring the movie 'deer hunter' to mind. It seems that even as far as metalurgical interest goes, making ferrite is the bottom of the barrel as far as work conditions.
Before someone says I am saying RF engineers are posh, I just mean its a dirty ass nasty job. My friend works in a factory that has a kind of department related to heat treating, kiln work, etc.. and it pays more to work in that location. Most people don't wanna do it, blue collar guys like mill wrights, stock workers, tool operators. Apparently it feels like walking into hell. But it means a hell bent individual can save alot of money.