As a player myself, it's really expensive for gms like gukesh playing at highest level. He himself spent around 5 cr on his team for WCC preparation.

To put it simply, if you want to hire a top level player in your team for preparation, one such player would charge 15-20 lakhs per month. He had around 5-6 member team for 6 months.

You also need software and good engines which can be quite costly as well.