It really depends on the £5 knife you are using as your comparison example. Most knives in that price bracket are junk, although Mora and Hultafors (plus 1 or 2 other maybe) seem to be able to make very good blades at that price point. A lot of folks don't get Mora (or the equivalent) at all, maybe it's the plastic sheaths or the fact they aren't full tang. Again this comes down to perception and what you need from the tool. I don't own a Mora (yet although I will be getting one in the future), I'm about to get a Hultafors GK for Fathers day from my son. It was a toss up between the GK and a Mora HD Companion. I went for the Hultafors GK as you can use it with a ferro rod straight from the box (sharp edged spine), and it's half the price of the Mora equivalent, without being half the knife. I will most likely replace the sheath with something that has a better means of attachment to a belt, and have the ability to mount a ferro rod. A more expensive knife would likely already have this.
What you are likely to get from a knife in the £30-50 range is a more refined blade with perhaps a full tang, better handle, better/more functional sheath. It will still be mass produced and there are still a lots of over priced garbage as well in that bracket. However there are some very expensive, hand made blades with wonderfully intricate leather work sheaths out there that have poor heat treatment and suffer poor edge retention as a result.