Do you like to comparison shop? You know, deciding what has greater value, makes more sense, has better appeal, is more desirable? Do you carry that comparison thing over to the value of others compared to yourself? Paul encourages the Galatians to honor all others and to keep their eyes fixed on the product of their life, to not compare.
While this begins addressing the benefit by the one taught the Word, it directly extends that expectation of benefit back to the one doing the teaching. The verses then go on with the teaching about sowing and reaping and how sowing is done in the expectation of production. It then expands the teaching to apply to life and discipleship, to growing in the Spirit of God and the expectation that disciple will grow. It is not presented as an option but as the result of being a disciple, to experiencing the discipline of the Holy Spirit upon our lives. But there is also a warning that not all sowing produces beneficial reaping.
There is a difference, a consequence, between the nature of our sowing—flesh to corruption versus Spirit to eternal life. The flesh is quite willing to continue sowing, using the old habits, ways, lifestyle to diminish the productivity for the LORD. This is not of the Holy Spirit but if your repentance of the former and commitment to the latter are not lived out in the Holy Spirit, corruption of possibilities is the outcome of living in the flesh.
The Apostle does encourage living in the Spirit, continuing in the Spirit, growing fruit in the Spirit, not letting up in being the disciplined 3 of God.
Paul concludes with the allusion back to the start of the passage and the ‘sharing of good things’ with the teacher. It is not a wrong thing to share the blessing of being taught well with the one doing the teaching. They may appreciate the encouragement just as you were blessed by what you were taught.