who are this "insiders"
The group admins and his close friends or people who paid him the high amount. These are the groups first slowly accumulate some cheap coins and later they release information to the general group and once people start buying then these guys start selling at a high price.
Do you know something about that or is a scam?
Most of them are a scam so don't waste your time and money in these groups instead learn yourself trading basics and start investing for a long term to make a good profit.