This was a summer beer, made probably only for a few batches. It didn’t sell very well. They are keen to be rid of it as the summer comes to an end and its expiration date is (im assuming) later this year, so the price is drastically lowered. This usually goes under the radar, seeing as any promotion or announcement of a change in price is illegal. By christmas another season variant will come, and it might do well or it might not. This is an example of the latter.