Why is comma placed after conjunction “since”?
Is it because the phrase *wanting…too stingy* is a parenthesis to modify “this”?

Restaurants increase the price of the second least expensive meal since, wanting to strike a balance between saving money and not appealing too stingy, this is the one customers tend to choose the most.

Question

Why is comma placed after conjunction “since”? 
Is it because the phrase *wanting…too stingy* is a parenthesis to modify “this”?

Restaurants increase the price of the second least expensive meal since, wanting to strike a balance between saving money and not appealing too stingy, this is the one customers tend to choose the most.

Answer

The commas after 'since' (or before 'wanting'l and after 'stingy' indicate that the clause they contain is removable. They serve a parenthetical function, yes.

Answer

it's not "after since", it's "before wanting" which is pointing out the process - ing

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!