As with every famous or reputable brand or product in the world there is a bad side on the success of a brand or product.
COUNTERFEIT !!!!!!

It cannot be disputed that CASIO is almost a household name as far as the calculators are concerned and the products manufactured by Casio are considered to be highly reliable and of superior quality. If the quality of the counterfeit products being sold under the trade mark CASIO is not found to be as good as the quality of genuine product manufactured and sold by the CASIO, this is likely to dilute the brand value of the trade mark CASIO and cause immense damage to the reputation and goodwill which CASIO enjoys in the market. The consumer buying a fake product on the assumption that it was a genuine product manufactured by CASIO, may, on finding the quality to be inferior, assume that the quality of the product being manufactured and sold by CASIO has gone down and that, in turn, may substantially impair the business interests of CASIO. Even otherwise, it is in the interest of the consumer as well that he does not buy a fake product bearing the trade mark CASIO in a mistaken belief that he was purchasing a genuine product.

It is sometimes difficult to see fake or real as even the packaging is copied.
One rule..... When the price is really cheaper than the original, you can be almost sure to buy a fake one.

On Ebay there are sellers from China, offering fake Casio calculators. Please don't buy them. India and China are the biggest producers of counterfeit Casio's.