I think LKY anticipated way ahead of his time that if the Ministers are not paid what they are worth especially when they are already earning more outside before they join the government, corruption will creep in eventually.
I overheard this from the grapevine. A journalist once asked LKY about the high ministerial pay in Singapore. He told her ," You may think I am the highest paid government minister , but I don't think I am the richest minister in the world."