I've read the dossier expenses were a bit north of $1M. The rest of money spent by the law firm was likely on campaign compliance issues.
If the information in the dossier was real, and obtained by real Russian sources, who maybe have to be bribed, or was the result of real surveillance, real manhours spent digging and following and whatnot, you can expect expenses to run into six figures.
But it wasn’t real, it was fiction. As such it could have been cranked out in an afternoon.
So, 12 million to Perkins Coie, who passed 9 million to Fusion, who passed six figures to Steele.
Lots of money unaccounted for.