Wagner group consists of more than 3600 persons, and the running cost (no definition of what that is) is 17.4 billion rubles.
It started 2013 as Slavonic Corps Ltd. in Hong Kong and offered salary of $5000 and were first opposed by the Russian State and FSB arrested their leaders. But soon Kremlin understood the value in having such a group and there were engaged both in Syria and in Donbas / Ukraine.
The fighters were transported by the 76th Airborne Division, Pskov Region, to Syria.
https://newizv.ru/news/politics/21-02-2018/uzhe-ne-tayna-stalo-izvestno-skolko-boytsov-v-chvk-vagner
Quoting Girkin/Strelkov, see above. But read the comments after the article:
it wasn’t just five Russians killed in the American raid – it was 218. (US officials have said about 100 pro-regime fighters were killed, without specifying whether they were Syrian army, Russian or other forces.)
However, the paramilitary chief said only 150 bodies have so far been recovered.
“There are 150 people in refrigerators on the Wagner base” back in Russia, he said. “Their state? ‘Minced meat’ is how they described them to me.”
Even so, the chief doesn’t feel much sympathy for those who died; he believes it is a fate they chose.
http://www.france24.com/en/20180223-russia-fighters-syria-exclusive-interview-mercenary-wagner
The next article is asking the typical Russian reaction: “Who is responsible”, and how it can be used by Putin.
http://censoru.net/24865-nashi-russkie-zhirinovskiy-progovorilsya-o-gibeli-vagnerovcev-v-sirii.html
According to the next article it was actually Russian SF and 257 are KIA.
https://www.segodnya.ua/world/russia/zavalili-kadrovyh-volonter-na-primere-razgroma-chvk-vagner-obyasnil-ischeznovenie-putina-1116623.html
An example of a deza article:
Actually it was Americans that died in Syria and it was due to our new Su-57: http://g-news.am/%D0%BC%D0%B5%D1%81%D1%82%D1%8C-%D0%B2%D0%B0%D0%B3%D0%BD%D0%B5%D1%80-%D1%81%D1%83-57-%D0%BA%D1%80%D0%BE%D1%88%D0%B8%D1%82-%D0%B3%D1%83%D1%82%D0%B5-%D1%87%D0%B2%D0%BA/