$$$ comes from unreleased token which are part of the token max supply. Liquidity providers can only stake LP token on PowerPool (which comes from the deposit of CVP released tokens and ETH on Uniswap) to get CVP token rewards which is a common practice known as liquidity mining.
Now, PowerPool has a token economy through CVP, but first to initiate token economy, tokens need to be released to the public, at least some of them. PowerPool has communicated the token allocation and release program that you can review at the following link: https://medium.com/powerpool/understanding-powerpools-cvp-token-model-7ad36ea66999
Within this table, the PowerPool team explains how tokens will be released and what is the token maximum supply. The token maximun supply of PowerPool is 100,000,000 CVP tokens. As you can see in the table in the referred link above, the team has explained the token release plan along with PowerPool app version release.
PowerPool is currently on Mainnet so we are at the mainnet liquidity mining stage, if I am correct, so the plan is to release 80,000,000 CVP tokens by granting rewards to the liquidity providers who stake their LP tokens.
According to coinmarketcap, PowerPool has a current circulating supply of 20,306,673 which means that we are at the very early stage of the liquidity mining program because only 306,673 CVP tokens (0,0038%) have been released through this incentives program. 20,000,000 CVP tokens were already released on Alpha round, Beta round, Gamma round and to the community pool and so available to provide liquidity.
In few words, it means that 4/5 of the token max supply will be released through liquidity mining program to max 1/5 of token max supply for the time being (which is the circulating supply). It also means that max 1/5 of token max supply holders could potentially earn 4/5 of token max supply with mining rewards.
So, to give you a quick answer, the rewards comes from the unreleased tokens that will be released to the public through incentives program. Then, the market values the token and turn it into $.
I hope it helps and clarifies.