Is Apple's Golden Goose About to Be Cooked?

NEW YORK (TheStreet) -- Even though Apple(AAPL) reported record second-quarter revenue and earnings, shares have given back all of their gains and then some. We now may have a reason why: It looks like the carriers are starting to fight back.

Apple depends so much on its iPhone for growth, which accounted for $22.7 billion in revenue, nearly 58% of quarterly revenue. It's Apple's largest product segment by far, and any dent in revenue could dent Apple's stock.

U.S. carriers Verizon(VZ) , AT&T(T) and Sprint(S) could either cut back on carrier subsidies or extend the life-cycle of their contracts, and evidence is mounting that it may happen.

Are the telecos about to put a worm into Apple's profit margins?

There are signs across the industry that carriers are becoming more disciplined with subsidies, Credit Suisse analyst Jonathan Chaplin thinks.

"If this discipline holds, we believe there is upside to margins and earnings growth for all carriers," Chaplin wrote in a research note. He upgraded AT&T and Verizon to outperform and raised his price targets to $36.50 and $45, respectively.

Most contracts for cell phone customers are about two years, and Chaplin noted that the upgrade eligibility has been pushed out over the past year, from around 13 months to around 20 months, while implementing upgrade fees to offset the subsidy paid to the handset makers. Apple's subsidy is exceptionally high, given the iPhone retails for $649 without the subsidy. The average subsidy on phones is around $265, but Chaplin thinks it could go as low as $250 per phone, as fees are added and eligibility gets pushed out.

While this is a potential negative for all handset makers, Credit Suisse analyst Kulbinder Garcha cut his estimates for Apple as evidence mounts of a shift in subsidies.

Garcha noted that North America counts for 38% of total units over the past six months for Apple, and cut his earnings estimates for 2012 and 2013 as a result.