For that matter, is spending equally high in every election year? There's a big difference in noise and media attention between an election year like 2000 or 2016 and an election year like 1984 or 2004. I assume that's reflected in the amount of spending (if nothing else, you simply have fewer big-pocketed candidates in the mix when a popular incumbent is running).

I'm definitely not an expert. Maybe it really does have a huge impact. But listing a few figures from a major primary season doesn't make that case.