The passage reads:

But after they had been away for longer than the agreed time, and Corobius had no provisions left, a Samian ship sailing for Egypt, whose captain was Colaeus, was driven off her course to Platea, where the Samians heard the whole story from Corobius and left him provisions for a year; they then put out to sea from the island and would have sailed to Egypt, but an easterly wind drove them from their course, and did not abate until they had passed through the Pillars of Heracles and came providentially to Tartessus. Now this was at that time an untapped market; hence, the Samians, of all the Greeks whom we know with certainty, brought back from it the greatest profit on their wares except Sostratus of Aegina, son of Laodamas; no one could compete with him. The Samians took six talents, a tenth of their profit, and made a bronze vessel with it, like an Argolic cauldron, with griffins' heads projecting from the rim all around; they set this up in their temple of Hera, supporting it with three colossal kneeling figures of bronze, each twelve feet high. What the Samians had done was the beginning of a close friendship between them and the men of Cyrene and Thera.

From what I've read, Sostratos is never mentioned again by either Herodotus or any other extant source, and I can't find much information about him online. Is anything else known about him?

I just find it to be such an intriguing anecdote. The most profitable Greek trader of all time! And that's all we know.