It is important to realize that the larger coupon sites such as Coupon Cabin, RetailMeNot, etc rely more heavily on placements from merchants than they do typical commission payouts for their revenue.
Generated sales for a given merchant may yield xxx/month in commissions (multiply this by hundreds or thousands of merchants), but ...
A specific placement on a category / homepage (in rotation or not) can bring in xx,xxx/day, week or month (depending on seasonality) with a flat fee / revshare or hybrid arrangement. Now multiply that
So traffic is vital to keep eyeballs looking at you when you are looking to ask that kind of money. Hence the willingness to accept negative operating costs in certain marketing channels when you know it will all back out in the end.
The one common denominator all the successful coupon sites have is age. I have seen some horrific looking sites that are so profitable that have been around for over 10 years. They are connected, have a decent amount of staff and are busy signing IO's 6-9 months out.
You want to compete with all that? Build something that offers at least one unique hook, and align your business model so that you can forecast all the expenses 1 year out and be willing to pay for eyeballs one way or another.
Define sales objectives that can pay for it all, and get busy with that phone ...
/2cents - Cheers