I would like to clarify that I also think the prices are quite high, or rather, exorbitant! Although the level of service is also commensurate.
And now, let's start working on the magic!
So, since we've decided to calculate for two people, and even for a comfortable stay in a 4-star hotel...
Let's start. My wife and I are more down-to-earth, so I'll rent half of a cottage. For this, I'll team up with another couple. The cottage has two levels, so that's not a problem. Furthermore, all calculations are for two people
Accommodation cost: 24,000 rubles
Banquet: 2500*2 = 5,000 rubles
Meals: I'll only take lunches for the following reasons: firstly, one of the days includes a full-day excursion; secondly, I hope we'll have barbecues in the evening; and thirdly, the cottage has a refrigerator and a stove, so we can easily organize some basic food, like sausages, dumplings, and other fast food for the evening. So, lunch for two people per day will cost 700 rubles. We'll exclude the day of the excursion and one of the days for arrival/departure/banquet, and we get 5*700 = 3,500 rubles
Conference/hall: - 3,500 rubles
Alcohol for the banquet: - 2,000 rubles
Total: 24,000 + 5,000 + 3,500 + 3,500 + 2,000 = 38,000 rubles/for two/19,000 per person
That's how it works out!
And I'll repeat once again, you can always cut back and save on logistics, alcohol, food, and so on. The main thing is the desire and ingenuity.

Also, as additional reference information, the CIS 2015 event in Volgograd cost 13,425 rubles without meals, and with accommodation in a simple and very modest standard. Add the cost of meals, and you'll get almost the same price, but with a higher quality of service