https://partner.steamgames.com/doc/sdk/uploading/distributing_source_engine said:
For any Source Engine game that charges money, Havok needs to be paid a licensing fee of $25,000 for the physics engine. You will need to pay this fee up front before making your game available for sale on Steam.
so they had 25 grand left from the get go and probably popped off 50-100 quid each for 10% of the models and animations they didnt steal or reuse from Valve games which i'll say is about 5 grand, maybe 7 or 8
another 3 or 4 for all the voice acting since theyre all too subpar and utter shit to be payed more than 50 quid, so theyd still have 10+ grand left over
im willing to bet Berkan either kept every penny of the left overs or it was all blown the party where a few of the people who helped realised how shit the game was and failed to convince Berkan to delay it several months, most likely the former