Wow, the crushed concrete is expensive comparing it to what I can get a load of #57's locally but like all things it matters where you're located. I can get a 25 ton load of #57's delivered on the cheap side at $350 a load to the high side of $500 depending on the location.
Some chert is great and some is so-so. 10 years ago had a project where we flat-topped a mountain ridge that was solid chert, 30' cuts in the deepest area. This was great material, even ran into seams of pure white sand in between the rock layers. You could dump it out of the truck, spread it with the 953 and achieve 98% compaction without putting a roller on it. The PCF was in the 128 range. Most chert has enough rock in it that it's not slippery or muddy when it's wet. In the winter it's about the only option for engineered fill other than crushed limestone which is obviously way more expensive.
We did the site work on a Sonic in Greenville, AL adjacent to I-65 years ago. Ran into some very black dirt that had to be undercut. We run into deep topsoil all the time but this was different, it had a sheen to it. The geotech said it would probably be the oldest dirt we'll ever move as it was the remnants of an ancient sea. The plumbers found a large sharks tooth when they were putting in the sewer line. Greenville is about 150 miles away from the gulf.