It's impossible to describe how the Twelve might have received this news. As Jews, they had longed for Messiah and had staked everything on Jesus being the Promised One. But there is an extension of this promise to all believers. I do not pretend to know all that this entails, but the promise is clear. In verse 29 the Lord established the principle of rewards.
Present sacrifice produces eternal privilege.
Everyone who has left houses or brothers or sisters or father or mother or children or fields for My sake will receive a hundred times as much and will inherit eternal life. Obviously, this equation is not to be pressed literally. No, the Lord's point is to say that there is a blessing both now and in eternity that is all out of proportion to the cost of discipleship. Following may not feel like it pays, but in God's time and way it certainly does. So the Lord summarized with two points.