"The staff costs far outweigh the income generated from being open," Mr Gray said.
"If council feels they want to be open on public holidays ... then council needs to say that's what we want and we're going to make the budget available."
Extending Glassworks opening days would require an extra permanent part-time assistant and a casual technical assistant.
Deputy mayor Jenny Duncan said there could be ways to extend opening days for less than $30,000.
"I think we should look at what days it's currently closed, particularly over that Christmas period," she said.
"I'm not in any way, shape or form saying it should be every day that it's currently closed.
"I'm sure the number will come in considerably below that $30,000.
"I don't necessarily expect that retail sales would match up with that so there will be an initial cost but I just think it's an exercise that's worth conducting."