Which of the following sentences is correctly punctuated?
1. The operating costs, as he probably told you are too high.
2. The operating costs as he probably told you, are too high.
3. The operating costs as he probably told you are too high.
4. The operating costs, as he probably told you, are too high.

Hi!!


The correctly punctuated sentence is: 
4. The operating costs, as he probably told you, are too high.

The rule is:
"Use commas around nonessential words that interrupt or add meaning
not needed to understand the main idea."


For reference see the following Powerpoint presentation:
"Use of commas and end of sentence punctuation":
http://dl.ccc.cccd.edu/classes/internet/english105/PowerPointSlides/ch11.ppt


I hope that this helps you. Feel free to request for a clarification
if you need it.

Regards,
livioflores-ga