Charles Ellicott Commentary 1 Thessalonians 2:8

"even so, being affectionately desirous of you, we were well pleased to impart unto you, not the gospel of God only, but also our own souls, because ye were become very dear to us." — 1 Thessalonians 2:8 (ASV)

So means here even so, confirming the simile, and is not to be taken in the sense of “therefore.”

Not the gospel of God only.—The gospel was, as it were, the milk given to the young converts; but the nursing mothers were ready to let them draw their very life away, so dearly did they love them.