Green Man Gaming has Tomb Raider for the PC on sale for just $13.60 right now. The price will show as $16.99 (66% off), but enter the voucher code GMG20-LLASD-D8WBQ to save another 20% off. This sale is valid for 24-hours only.
All prices on GMG are in US dollars and exclude tax. You will need to sign up for a free account there and they will email you your serial number.
This is a Steamworks game and will require a free Steam account in order to play the game.
Considering the game just released back in March, this is a very good price.