What I say,"当做插入语理解相当于下面几个短语

(1)as far as I am concerned

(2)in my opinion

(3)in my point of view

(4)in my personal point of view

(5)personally-speaking

(6)I think

     ......

     'You told that old beggar all my private affairs?' cried Hughie, looking very red and angry. 
     'My dear boy,' said Trevor, smiling, 'that old beggar, as you call him, is one of the richest men in Europe. He could buy all London to-morrow without overdrawing his account. He has a house in every capital, dines off gold plate, and can prevent Russia going to war when he chooses.' 

    'What on earth do you mean?' exclaimed Hughie. 
     'What I say,' said Trevor. 'The old man you saw to-day in the studio was Baron Hausberg. He is a great friend of mine, buys all my pictures and that sort of thing, and gave me a commission a month ago to paint him as a beggar.

    ......

从上下文可以清楚看出，what I say并非“在我看来：我的看法是”，这种解释放在语境中是不通的。

根据上下文，what I say应为what I am saying is. 至于这种用法是否规范，也不必追究。词典查不到这种用法。根据上下文能猜出其意思就足够了。