costliest

ˈkɒs(t)li

adjective

costing a lot; expensive.

major problems requiring costly repairs

expensive,dear,high-cost,high-priced,highly priced,big-budget,overpriced,exorbitant,extortionate,immoderate,extravagant,lavish,rich,deluxe,choice,fine,exquisite,valuable,priceless,worth its weight in gold,worth a king’s ransom,upmarket,over the odds,steep,pricey