By quite a bit I'd think. I've had versions of this conversation before, both online stemming from situations such as this Tree House one (Birds Fly South, a small brewery in SC, has brought up this issue on their social media pages a few times), and in person with friends opening a brewery who were debating glassware strategy. Both anecdotally and based on data that breweries have reported, customers are -much- less likely to steal a glass if they are given the option to purchase it. It's only when their only option to obtain the glass is to walk off with it that such a thing happens regularly. Like
Gene, not saying that's right at all (it's not), but it's what happens. One of the most common self-justifications I've heard others use is that they leave an additional tip of 10 bucks or something in that range to make up for the cost of the glass. Obviously that doesn't make it okay, but it does seem to indicate that the hypothetical cost of the glass isn't the reason they are stealing it.