I'm the same way, most of the time. But I think many (most?) people are not. Also, even if they are, it's really hard to visualize large sums of money, so spending $1B on something is really hard to reason about.

But I think it makes sense in general. If I were to buy something with someone else's money for someone else, I honestly wouldn't care too much about either the cost or the gift, I'd get the thing that seemed reasonable to both parties. For example, if I bought gift for someone who performed a service for my company, using my company's money, I would not be very cost conscious, and I'd only put minimal effort in (after all, it's just a task I need to complete). I don't want to be stingy (we want the person to like us), but I also don't want to get flak from accounting.