Hi Dips! In my experience buying the best you can afford does help, but a lot of it is to do with your own hair type and personal aptitude for styling hair. When I had short pixie hair I could get away with any old hairdryer, but now my hair is very long, thick and curly a cheap hairdryer destroys it.
I've used many types of hairdryers as I did a hairstyling course (blow dries and up-dos, not cutting) and style my friends and families if they ask me, therefore using their hairdryers that they have in their homes.
There isn't much difference in the mid range £30-£60, but above that you will get better speeds, quality and features that ultimately aid styling and condition. But the tools you use will make a difference too Dips , the right type of brush makes a difference too.
Hope that helps!
I do like the look of this dryer, but the whole presentation was just me me me from Jill Franks, talking about her supposedly long, volumous hair. Sigh.