If you can't afford Ruth Chris, don't go to Ruth Chris.
If you tell your date, "don't worry, help yourself" (whether you really mean it or are just saying it--I always tell people NOT to say things just to be saying it) don't get mad if your date doesn't worry and helps herself/himself.
It really depends on a few factors. The smart thing is to go with the flow and order in the range that the person who is paying for it is ordering--unless the person tells you differently.
When my significant other and I were "just dating" we went to a range of types of restaurants in terms of costs. He usually "helped himself" and was insulted if I did not "help myself." He considered it disrespectful and a challenge to his sincerity (i.e., second guessing what he means by "help yourself"), aspects of his masculinity, and even his salary range for me to buy something cheaper when what I really wanted was the more expensive item.
When the "just dating" became a significant other relationship, being cost effective was more valued and appreciated.
