yes .. it scam .. there is many site like that.
there was a thread about site like startminer, you can search it
yes, i agree too, i don't know all of them but i guess a large number of these sites are scams.there was a thread about site like startminer, you can search it
moreover its sure they don't pay all their members even if you pay an upgrade (i saw many comments about this last year)
and i tried one of these site as free member, first payment never received
They probably pay few upgraded members to attract more people to buy their upgrade but i don't think you will get your investment back (if u buy upgrade).
to earn free coins : faucets and bticoin ptcs are safer way (captcha aer boring i know)
https://www.wibudincome.net/my-faucet-list
https://www.wibudincome.net/myptclist
Theres no guarantee you will get your investment back will all sites that requires an investment