Except that is not the case at all. The Super PACs backing Walker and Perry were not Super PACs like the Koch Brothers' Americans for Prosperity or Karl Rove's Crossroads USA. These were Super PACs that were specifically designed to only support one candidate and only candidate only. And they had plenty of cash. And they were very willing to spend it. Insiders from both within the Unintimidated PAC and the Opportunity & Freedom PAC have both stated that they were very willing to go all the way and were very upset that their candidates dropped out.
Alot of these Billionaire Sugar Daddy PACs, the money is given to them with conditions on it(and I am guessing some said don't use this money until...). You cant say these PACs don't make some difference when not much of the cash they collected was actually used. You can't tell me that Walker wouldn't be int he race and his polling numbers would be much better if his PAC didn't decide to spend half of it's cash right away for instance