If you've got a team of smart people willing to drop $500k on a banner campaign and you can accurately measure the results and it's still worth it with all the fraud, good for you. If you're a mom and pop store looking to spend $500 on advertisements they should be made aware there's a good chance they will be defrauded unless they know what they are doing.
This is really important. I really believe small-time projects have no business buying advertising online. It's just so incredibly low value that to scale it to meaningful results takes a lot more money than a person or small group of people bootstrapping their project on a shoestring can muster. For example: my wife has written a sci-fi novel. You can buy an eBook or paperback on Amazon. We would have to spend a few…
The basic statistics to calculate the RoI on a banner ad spend isn't particularly difficult when you have a software dev/web dev available.
No matter how much click/impression fraud there is...you are trying to track conversions not clicks/impressions at that scale.
If I know I spend $500 and get 10 sales, it isn't a statistically valid sample but its pretty clear if I break even on that $500...I should keep doing it since its essentially free marketing. Similarly, if I'm willing to eat $N per customer acquired via marketing, the same is true as long as $50/customer is equal to or less than my margin per sale + $N. "Sale" in this context is tracking what exactly those 10 people bought over the lifetime of them being a customer, generally.
The only real thing the "already successful" people have is a bunch of smoke and mirrors that honestly doesn't have verifiable value that they use to bullshit clients. Conversion rate is literally the only statistic that is verifiable, cost effective to verify, and able to give you a concrete idea of whether or not the RoI of the campaign is worth it.
We have an on staff statistician and his primary job is just automating the conversion rate calculations, the return-per-ad-campaign, etc. We spend enough money its worth hiring a staff statistician to do that but honestly any programmer with a book on statistics would 90% as good.