(IDEX Online) - Billionaire Amazon boss Jeff Bezos has presented his fiancee Lauren Sanchez with a huge diamond engagement ring, estimated at up to 30 carats and valued at up to $5m, according to US media reports.Bezos, 59, proposed to his long-term girlfriend on his $500m superyacht the Koru during a Mediterranean vacation. Divorced Sanchez, 58, is a US media personality and former TV news anchor.There has been frenzied speculation in celebrity magazines about the exact size and price of the "monster rock", with estimates from 20 to 30 carats and price from $2.5m to $5m, but thetre are no definitive details.Not that the expense is likely to trouble divorced Bezos, with a fortune estimated by Forbes at $145bn.Pic shows Bezos and Sanchez