If they've been doing this for a long period of time and on many projects then they are just busted with OP's revelation, other projects should come here to support OP's allegations, scammers are willing to pay that amount if they are going to get more money from these reviews.
They are guilty of supporting scammers if positive reviews are being paid, they even fooled people by posting on their site that they do not receive payment, they deserve a negative tag and a flag.