That means of course, taking in to account that I provide 5 retouches, each in Colour and BW versions, that you are actually paying for 6 hours minimum (1 for the shoot and 5 for the editing). This doesn't factor in the fact that shoots often run over time, edits can take longer, equipment set up and pack down takes a mo on it's own, and organising the shoot takes it's own time; but let's ignore that and say that actually I am now charging you £150 / 6 hours = £25 per hour.
This assumes of course that you were only paying me for time, but as many photographers have pointed out on many blogs over the last few years we have to cover costs like insurance, gear purchases and repairs, website hosting, taxes, internet, software, and the list goes on.
I don't tell you this to complain, but I hope this gives you a better idea of the hard work and skill which goes into creating the portraits or headshots you're parting with your hard earned cash to obtain. The session you are involved in is only really the tip of the iceberg.
I usually end up telling people who ask the question which started this post, that I'm very proud of the work I do to produce these images, and I stand by my pricing as I believe they are worth every penny.
Having peeked behind the curtain, I hope you now do too.