Some people think that just because you don't have to pay for something it devalues that something.
The gift of God is Eternal Life through Jesus Christ our Lord. (Rom 6:23)
Beware of those who sell a product rather than give it away. The transaction will always benefit the seller and may or may not benefit the purchaser.
A seller tries to make his product appeal to the masses to increase his revenue. Books often are tailored to the masses for that very reason.
Strait is the gate and narrow is the way that leads to life. (Mat 7:14)
I ( Jesus) am the Way, the Truth and the Life. No man comes to the Father but by me. (Joh 14:6)
It is only in Christ that we find a completely non-mercenary purveyor. He gives us Himself and we receive Him freely.
He is the pearl of great price. He is the treasure hidden in a field. (Mat 13:46 Mat 13:44)
Since we sell all that we have to purchase the pearl, the treasure, it may sound Mercenary. But what we were before Christ is totally worthless. We had nothing to offer.
And all we can offer now is our body as a Living Sacrifice to Thank, to Praise, to Testify and to Worship our Lord Jesus Christ.