Jennifer Aniston and Justin Theroux have not even walked down the aisle yet, but Theroux is already spoiling his bride-to-be with expensive and lavish gifts.

Theroux, 41, picked up a surprise present for his 43-year-old fiancé last week, and he paid a pretty penny for it, The National Enquirer reported.

The actor and writer headed to the Beverly Hills location of Tiffany & Co. after a business meeting to find a gift for his future wife.

He quickly found the perfect present - a "platinum heart pendant covered with sparkling sapphires." But the price tag - a whopping $15,000 - startled Theroux a bit.

"Justin thought the necklace was a couple of thousand - and went into shock when the saleswoman told him it was just more than $15,000," a sourced told The National Enquirer. "He took a big gulp, pondered a minute, then said, 'Oh what the hell!' He told the woman to wrap the bauble, saying he'd save it for a special occasion."

Perhaps the gift is meant to be a pick-me-up after the spats the couple has reportedly had over the plans for their upcoming nuptials. The couple allegedly argued recently when Theroux wanted to invite his ex-girlfriend, Heidi Bivens, to the wedding.

"[Justin] must have had a 'brain fade' moment. Jennifer hit the roof when she saw that he'd put Heidi on the guest list," an insider said. "Jen snapped back, saying she was going to invite her exes John Mayer, Brad Pitt and Vince Vaughn. That seemed to help resolve things because now they've agreed no exes are to be invited."

Theroux isn't the only one dropping serious cash in advance of the wedding. Aniston recently spent more than $2,000 on a luxurious customized skin rejuvenation treatment at the Beverly Hills skin care center Mila Moursi.

The Mila Moursi website lists the customizable rejuvenation treatment with a price tag that starts at $1,850.

"Our exclusive method has been proven to minimize the aging process, nourish and rejuvenate devitalized or sun-damaged skin, help lift and contour the face. Regular treatments reduce the appearance of fine lines and wrinkles, and help maintain a firm, glowing skin," the website description says.