Ex: Ad Rev/Sales = $100 Cost of Sales= $70 Gross Profit = $30
So, the IRS is only going to see that you earned the 30% either way. The only real important issue you may want to consider is whether you want your gross sales to be so high. Have a large amount of gross sales could exclude you from a number of small-business tax saving options such as the S-Corp election and it would make you have to file much more complicated tax returns. If you have a large amount of sales (millions) then you'd have to file reconciling schedules between accrual accounting per your books and records to your tax records.
Honestly, there's an unlimited number of possible problems when you start making lots of money. Mo money, mo problems. But, lets worry about making that first buck and take it step by step.
Conclusion, dont worry about it until you get there because you're fine so far.