Hi Jorg,
First of all regarding Volgograd, no unfortinately it is not a popular location for cycle touring. Perhaps some locals who live in that area are travling around, but for others there are no points of interest apart of Mamaev Kurgan you mentioned which is a part of Volgograd city.
The money shown in the table is the start fee which everyone pays, basically they cover trip registration with Ukranian National Federation of Tourism as well as organisaninal expanses. It does not cover any expenses you bear during trip (food, museums tickets, etc.)You will have bring your bike with pannier rack and proper bags with you, a tent and a sleeping bag. Also if you will be traveling by national rail in Ukraine, you will need a bike cover. Regarding food, it could be organised either so that you share food expanses with others (the usual way), or you may feed yourself on your own (this is popular among vegeterians). Food is cooked on fire, usually everyone participate in cooking and long dinner and talks near the fire at night. The advantage on traveling with Dneproveloklub, it that you will be guided by professional tourist, you will not have to think about where to set up a tent, thus there will be a lot of time to watch historic sites, monasteries and other interesting stuff.