A: 你看，那个人___高啊！ B: 这电脑___贵啊！ in this two sentence ， 好 and 多 is similar. but it is better to use 好 in oral language， because using 多 sounds like a question .这台电脑多贵啊！and 这台电脑多贵啊？ sounds like similar.

For the example sentences you proivded, you could use 多, but 好 is more natural. As you have probably notice 多 can be used in various ways . You can use it to express quantity, you can you use to express the English "how" and "much" Example 1: 你看他多有錢 "look HOW rich he is (when compared to you)" Example 2: 他比你有錢多了 "he is MUCH richer than you."

I agree that 好 is preferable to 多 as stated by the commentators, but just to confirm, you must have already considered 很, have excluded it for a certain reason, and prefer to consider 好 as opposed to 多? I would have thought that using 很 seems more typical in Mandarin and using 好 seems more typical in Cantonese: Mandarin A: 你看，那个人很高啊！ B: 这电脑很贵啊！ Cantonese A: 你看，那个人好高啊！ B: 这电脑好贵啊！ Of course, I could be mistaken, but this has been my experience over the past few years.

两个都可以用，但是就这两句话来说，我们还是更多地用 “ 好 ” 。

两个都可以用，但是这两句话在口语里我们还是更多地用 “ 好 ” 。