The lowest quote I received for the best injected preventative and kill was $304. In addition, this highly referred tree specialist company whom I've used before told me UNEQUIVOCALLY... the borer has NOT hit Denver, there has been no sighting here and no trees here have been affected. In addition, the best time of year to inject is from April to June, so that during the leaf out period, the application is moved throughout the tree. The companies that are pushing it NOW and throughout the summer and fall... at HIGH prices are simply taking advantage of concerned citizens.  Do what you want but I'm waiting till next April and hiring the reputable local company with whom I had an excellent conversation.