Amid slowing sales of Samsung's flagship smartphone, the Galaxy S4, numerous industry analysts have stated that many of the rosy sales projections initially forecast for the device were more than a bit optimistic.

Despite selling over 10 million Galaxy S4's in April alone, sales estimates for the device have been slashed by 30 percent by many analysts, costing Samsung almost $20 billion in just a week as shares plummeted.

"I'd say most forecasters including myself had this conviction that they'll outperform again - because it's Samsung," said Byun Hanjoon, an analyst at KB Investment & Securities. "They had beaten expectations before, which led many to believe they are bound to excel again with the S4."

Many early projections were based on the strength of the Galaxy S4's debut, but that momentum appeared to fizzle out after the first month of sales.

"The Street, including Goldman Sachs, admittedly extrapolated the first-quarter earnings momentum through the year," Goldman Sachs analyst Michael Bang said in a report. "This resulted in very optimistic earnings expectations."

For its part, the company says everything is going according to plan. The CEO of Samsung Electronics argued that the cuts in sales projections are the result of industry analysts' own mistaken estimates. 

"I can say sales of the Galaxy S4 smartphone are fine. It's been selling well," Shin Jong-kyun told reporters last Wednesday at the company's office in southern Seoul. "The report (by JPMorgan) was based on its own analysis. Probably, the bank may have corrected its previous bullish estimate about the S4 sales."

Industry analysts cited lower-than-expected sales figures as well as slowing growth in the high-end smartphone market among the reasons for the downgrade. The ongoing patent wars between Samsung and Apple were also a factor, as well as concerns that the Galaxy S4 simply doesn't have enough "wow" factor.