Climbing the ladder of value or just inflation?

I was just about to trash the copy of my invoice that I referenced in my last post when I noticed the rate I was charging back in 1998. It was only a few pence over half my current rate now, and coincidentally I’m back working for the same client as then. I wonder, have I climbed the ladder and am that much more valuable to my client, or is it just the effects of inflation?

My super inflated ego votes for value, but it’s probably just inflation.