I can understand why you query the cost. When I started to use sticks I bought a pair (aliminium) for a tenner, from a shop in Keswick. They worked fine until I wanted to move 'up' in quality. I managed to buy a 'better' pair (aluminimum again) for around £40 (retail they were about £100) but I didn't notice any difference in any way between the 'cheap' model and the 'expensive' one! I then wanted to move 'up' again, this time to carbon fibre. It was just a 'I want' consumer thing! I noted an Immeadiate difference however, they were lighter than the aliminium ones but still did the same job as my cheap sticks. They were from Alpkit, they only cost £40. Then I broke one (across a charging cows head, didn't stop her, she still biffed me!) and then snapped another one which became stuck between two rocks. I almost bought a new cheap pair but then decided to splash out on Pacerpoles. It was Percy's fault, he let me borrow his for a short time, last year at the Glenridding meet, after 10 minutes I was sold!
I bought the carbon fibre Pacerpoles, I thought they were expensive, about £90 and they still do the same job, but the holding position is different, which totally personally prefer.
On the the flat, I do not have to use them, but I am often too bone idle to put them away. They are very helpful if you fancy 'swaggering with a jaunty air' for a while, or feel the need to have them to hand to deter cows or wayward farmyard dogs.
For me, they prove to be the most useful on ascents, but especially descents. Due to the Pacerpoles hand grip design I can now push down on them to help me, rather than having to pull myself up, could make my arms ache as well. When I used standard grip poles I never felt properly in control, especially when climbing down. With the Pacerpoles I just feel they help me more when descending. One thing I have learned however is when coming down, make sure the pole sections are properly tightened, otherwise your body weight can make them become shorter than you want them to be. Not well explained but its all to do with the grip!!!