Are you paying for the junk leads?
You definitely are... Your sales people wastes lot of time servicing junk leads which is a huge cost to company. Deploying a call center is less expensive but it's a fixed overhead and it might even spoil customer experience.
From advertising, to generating leads and servicing them, you incur costs at every level and it's really exorbitant. But, when you realize that many responses are fake, it makes your efforts seem unreasonable. The true cost of business conversion is estimated only when you factor-in all these costs.
If the quality of lead can be determined as soon as it arrives, you can easily save 80% - 90% of these costs. Moreover, it will spare you from the hassles of working with excel sheets & call center personnel.