By the way, please provide an estimate of the costs per person, excluding airfare (I've already found the tickets). Preferably a detailed one.

2 Merlin.
A large new topic about the final will be posted later. Excluding costs – we'll calculate.

Let's assume a person decides to play for all five days. They arrive on the 30th, then the 1st, 2nd, 3rd, and on the morning of the 4th of May, they can collect their belongings and go to the club to catch a train from there (a 5-minute walk from the club, one bus stop away).
Since they didn't stay on the fifth day, it's 4 days x 500 rubles = 2,000 rubles for accommodation.

Food in the city is very cheap. You can also eat at the sanatorium's cafeteria; I'll find out all the prices there. I'll go to this sanatorium tomorrow and check everything out.