Green Man Gaming has Tomb Raider for the PC on sale for just $20 right now. The price will show as $24.99 (50% off), but enter the voucher code GMG20-GGN5D-FC3NA to save another 20% off.
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 good price if you want to play the game now.