Ah OK, after reading their docs I see they've changed what "slots" used to mean in Dremel (internal version of BQ). It used to be that slots _guaranteed_ capacity, but did not limit it. Meaning that you could rely on having a certain number of workers in the cluster when you issue a query, but if Dremel had more it'd give you all it's got. Obviously this is not viable when people have to pay per terabyte read, because a ton can be read.

What they have now strikes me as an even better solution to the problem of bankrupting someone with a query IMO. Not sure how pricing compares to redshift et al, but pricing is the easiest thing for Google to change.