It is obscene how much money is spent on elections. But at a certain point, I don't think it matters, you either have enough money to run your campaign or you do not. $50 million dollars, it's still a ton of money.
We have been led to believe that ad saturation in tightly contested races is how to win. Oddly, there is research showing that the most effective advertising targets non-competitive areas, especially if the advertising is positive. These tightly contested areas, ads just seem to cancel out each other. It would be interesting to study turnout and voting patterns in non-urban areas of GA, and how each candidate spent money there, and how much.
What is actually more disgusting than what you cited is outside money. Actual donations to the candidate, either people want to donate or they do not (and let's be real, it is likely many Republicans knew donating to Walker was flushing money down the toilet), and $2900 limit, it's not like people really buy a candidate. The PAC money and dark money, Jesus Christ who knows who and how much. I find it very untasteful.