Samsung Electronics and LG Display supply memory chips and displays for Apple’s newest iPhone and those components are among the most expensive parts in the hot-selling smartphone, iSuppli said on Monday.

The much-touted display of the iPhone 4G is the costliest component, being priced at $28.5 and making up 15.2 percent of the product’s total costs, according to estimates by the market research firm.

iSuppli said LG Display, the world’s No. 2 display maker, is the “most likely supplier” for the iPhone 4G display, along with Toshiba Mobile Display. The 3.5-inch “Retina” display boasts a 960 by 630 resolution -- four times that of the iPhone 3GS.

Samsung Electronics, the world’s No. 1 memory-chip maker, supplies the next costliest component for the newest iPhone -- NAND flash memory, which costs $27 and accounts for 14.4 percent of the BOM in the 16 gigabyte version of the iPhone 4.

Samsung also produces the third-most expensive part -- the 4 gigabits of mobile DDR SDRAM, priced at $13.8 or 7.4 percent of the BOM.

Samsung also makes the phone’s applications processor, which is priced at $10.75.

Apple is one of the biggest clients of both Samsung and LG Display. The latest iPhone, which was launched last week, is soaring in popularity, with sales passing 1.7 million units in only three days, according to Apple on Monday.

iSuppli expected Apple to continue to enjoy high profit margins from its iPhone sales, estimating the BOM of the latest model at $187.51, compared with $170.80 for its predecessor iPhone 3GS.