Yeah, I didn't specify Hamilton County, but the greater Cincinnati area. That said, given that HamCo alone accounts for more than a third of the MSA's population, I would not be surprised if the majority of regular PBS-goers are HamCo residents.
As for the "material just lying around," well, things like steel and concrete are commodities. I can assure you U.S. Steel isn't waiting around for Mike Brown to call in an order before they fire up the blast furnace. I'm sure there were items that were custom orders (I doubt that you can just buy one of those big-assed stadium video screen at Wal Mart) so someone(s) got paid to do that. Probably not local tho.
Workers just sitting around? Well, that's kind of my point: outside of a major economic downturn there are usually construction projects going on, so it's unlikely that any given worker's ability to draw a wage and pay taxes will be impacted by a stadium project. Might they make more or less on project X versus project Stadium? Sure, but now again we are getting into a discussion of goals/needs/level of support etc. Is "increasing the average hourly wage for construction workers" a goal for the public entity financing a project? If so then providing public funding with the "string" of a prevailing wage requirement attached might be worthwhile.