Hmm, I feel that's there's always some level of expectation when I'm invited to an event. Especially when I show particular interesting in certain items. I have been asked if I'm going to make a purchase at the end, and have politely declined explaining that I take a long time to make a decision on my purchases. If I'm invited by the same house to additional events, I usually decline because I've seen what I wanted to see and will still take my time making a decision.
I only go to events when I have interest in a certain collection or certain pieces. Sometimes I do buy on the day of and sometimes I don't. However, I generally don't go to events that I have no interest in. While my SAs are kind and often encourage me to go whether I'm interested or not, or will buy or not, I know that the hope is that I buy something and I'm not there to give false hope especially when I know what I like and don't like.
If it's a sort of "maybe" situation, for example, I'm not sure if I will like what's at the event, or I don't know much about what's going to be presented but I'm curious, then I decide based on my relationship with my SA. If I have a longstanding relationship with my SA who understands my tastes and shopping habits, it will not bother them if I choose not to buy, then I will go just to satisfy my curiosity. Maybe I will end up liking it and buy something. Maybe I'll learn something new and take it into consideration. Who knows!