This really isn't that complicated. The key for any business is to cross sell. If you are a restaurant and you know that your average bill is $80 + TIP you put out an offer $15 for $30 which is still a decent deal. You make sure your waiter works his ass off to get the up sells. Of course don't be to forward about it but you know instead of a $30 bottle of wine have him push the upgrade to a $40 bottle.
If your a hair salon doing a cut, offer the customer a die, blower, shampoo, conditioner, treatment, etc to at the very least make a few bucks on each one. That way you don't loose money. You don't make as much as you always do, but you'll have volume and you WILL get returning customers if you do it right.
The model works to get customers in the door. You just need to figure out how to convert those fuckers when they walk in the door.
The problem is tons of businesses are running deals to 'save' their business but reality is in MOST cases it won't for 2 reasons.
1. The deals cost money and the check they get will help them pay their bills this month but not in 3 months when the cost of services start to catch up.
2. The business owners are basically failing at their businesses anyway as that is why they are almost out of business so no matter what kind of advertising you do, if you don't run your business right you will FAIL. These people have no place running a deal in the first place, but unfortunately deal sites don't have a magic ball to know this before the deal runs.