From their web page:
The brokers' beer market is unique in Berlin. Situated in the Schiffbauerdamm 8, a house full of tradition, there are no set prices for most of the 18 German premium draught beers on offer.
Every day at 5 p.m. the regular beer prices are forgotten and new prices are regulated by supply and demand, as on the real stock market.
The rules are easy to understand: your order is placed on the market computer, which permanently updates the price of each individual beer according to demand. This means that you can pay any price from EUR 1.60 upwards and there's no limit! The beers that are not in great demand are more reasonably priced and therefore find favour with our guests.
You can observe how the price of your favourite beer is developing on monitors all over the Berlin Republic, so that you know what you have to pay when ordering.
A good chance for speculators!!
You pay the price which is shown on the monitor when you order. You then receive a coupon showing the price at the moment you placed your order. This is the price you pay when the waiter brings your beer, even if the price has risen in the meantime, partly of course due to the increase in demand your order has caused.
The market crash – good news for speculators!
Now and again, depending on the activities of the beer trade, the market crashes and the prices fall rapidly. So make sure to watch the development of the courses on the monitor and place a quick order.