I'm not sure I agree with your statement that "Having said this" (note that in BrE, it's normally "Having said that") means "I differ from my previous opinion". It means more that what you are about to say might not fit entirely with what you just said. For example "I love all soup. Having said that, the soup we had at the restaurant last night was horrible!" As you can see, I haven't changed my opinion but the fact that I didn't like last night's soup does make my first statement clearly not entirely true.
As far as your example goes, you have used it correctly for your context. Whatever it is that you said just before the sentence you quoted will cause the listener to now count you among his/her miser friends.
Student or Learner