I was very lucky, I got in on the “ground floor” with the addons I use daily, back when they were demo concepts, so paid very little indeed for them. Overall, for Blender, I doubt I’ve spent £100 all told. However, for CG in general, over the years, I have spent a LOT of money, on the purchase and many upgrades to Lightwave3D, subscription to the Substance source site for nearly 2 years, various books, dvds etc.
I simply don’t have that sort of cash now, which is what makes working Blender such a joy, as I simply don’t need to spend much at all. The biggest costs now come from any possible hardware upgrades. There are so many free addons for Blender and a wealth of free training that if you are on a tight budget, you can still get the job done.
Though if you are going to spend money on addons, have to say, Hard Ops, BoxCutter, Kit Ops and Decal Machine are what I consider essential purchases. They are almost illegal they’re that much fun!