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Nobody can help if you don't provide details. There can be many things you are doing wrong. Not targeting the proper people for one. Clicks mean nothing (free or paid) if those coming to your site have no interest or don't find what they are looking for. If you are getting clicks, don't assume you will make sales.
May be you have chosen irrelevant keywords or the set-up may not be properly configured. Check out with these so that you might get some idea.
You should try to re-optimize your campaign, maybe you have many things that you did wrong such as: wrong targeting, wrong keywords, bad landing page, fraud clicks, too low budget, ... try to list down each and optimize again step by step.
Go only with search (text ads) . On display there is a high rate of fraud clicks. I know google is fighting this and adwords is the best as a advertising program but there is a high rate of fraud clicks on display.
Thank you for answers, i've got 2 sales and it is very good, but product that i sell gives me 65 dollar for comission, i have around 1.5-2 percent conversion rate and cpc of 1 - 1.5 dollars for per click, i still can't make good ROI, but i think it is very important that i've got sales, what do you think? is there any way to get cpc around 0.3 for 1 dollar keywords? I have quality score of 10 for some keywords, can it help to decrease cpc?
The good news is that you have a QS of 10. This points to properly targeting your prospects (keywords, location) and that you have ads that are doing their job at getting the clicks. Not only that, with a great QS, you are protecting yourself from competitors: it makes it harder to overtake you. Now the reason it costs what it does is because that's the going rate for whatever keywords you are targeting. It's the free market at work. Think of it this way: those selling the same or similar products as you have no problem paying that much. If they were not profiting at that price, the CPC would be lower. And as you find out, to remain visible and make sales, you need to follow them and bid just as much. The way to lower CPCs is to have even better ads. QS is tied to CTR so you need to increase your relative CTR. Hard to do when you already have a high QS but it can be done. This may reduce CPC slightly but even if not, if successful you protect yourself even more. Think of the poor schmuck with a QS of 5 or 6 who needs to bid much higher to outrank you and is paying more because you have a higher quality. I think your main problem is your landing page not converting well. That's where I'd put my efforts right now.
Looks like you are very experienced, it is very good, this is my affiliate site example, I just did not added links but it is same as all my landing pages, what do you think is it normal? http://health-today.us/verified-products/
"////" this is the problem details. Really? Please don't spam! Now back to your title. It could happen because of many reason. It may be cause you choose a wrong keywords or for your your website design.