Exemestane Tabs 25mg 30 is one of those products which experiences regular price spikes. These have occurred three times now since launch in July 2011, have necessitated concession prices, and there does seem to be a regular pattern.
Although the number of months varies a bit between the spikes, when we plot the spike number (1,2,3,4) against the month since launch (1, 43, 73, 107) we get a straight line. This allows us to make predictions, such as saying that the next spike (after the current one) can be expected in about Feb 23, and the one after that in about Jan 26.
This data comes from https://www.wavedata.net/ and from https://www.bppi.co.uk/