Why do Generic Drugs cost less?

Generic Drugs like generic viagra , kamagra , penegra are much cheaper than their brand versions.
And more over these generic drugs are as much efeective as their brand names.
So why do these generic drugs cost less..Here is the reason behind this:

Manufactured and dispensed without a brand name, generic brands, also known as generic drugs are marketed comparatively at low price. Generic drug manufacturers are able to eschew their costs incurred by a saving the cost pertaining to research and development, regulatory approval and promotion cost.

A large portion of the cost of brand name drugs covers the high cost of research and development. Generic manufacturers do not have to duplicate the cost of research and marketing conducted by the original manufacturer. Therefore, the cost of the generic drug is usually less. Brand-name drugs require more time and money for initial research. This cost is incorporated in the total pricing of the drug sold to the consumer. On the other hand, generic drugs require less time and money for research, costing consumers 30% to 40% less on average.
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