This must be a new thing, because I've experienced the opposite. I needed to book 7 tickets, and the price was much higher than a single ticket. So I ended up adjusting the quantity and saw the price increase at around 4 tickets. So I ended up splitting the purchase into two transactions. However, after purchasing the first 4 tickets, the following price for single ticket was now slightly increased - so they were really playing some games or perhaps there was limited availability that was adjusting prices real-time.