Tom's Hardware writes other processors suffer the same fate. The Core i5-8400 for instance went from $182 to $225:
The Core i5-8400 is another processor that has suffered the same fate as the Core i7-8700K. Retailers have upped the price for the Core i5-8400 from $182 to $225, which represents a 23.6 percent increase.The shortage of Intel's processors may continue until the second half of 2019 so further price increases could be in store. This increases the competitive position of AMD, as you can get a Ryzen 7 2700X for $300. It has somewhat lower gaming performance than the 8700K though, but as the latter gets more expensive that may become irrelevant.