Funnily enough, I've been pondering this equation myself recently.
I tried on quite a lot of cheaper boots - Hi Tec, Regatta, Karrimor, for example - along with higher priced models. Although on the face of it there were savings to be had, only one pair of all I tried on actually felt comfortable. Aside from that, I had some doubts about durability as well. So, even though cheaper, I thought if they fail inside 1 year, or the soles wear out, or they hurt my feet, I'd still be better off going for better boots with a longer life expectancy and getting the same (or even better) value for money due to their longer life.
In the end I bought 2 pairs of boots - one more for summer/drier days, the other for the winter months and wetter days for £190 for the 2 pairs. I won't say which brands/models as what suits me probably won't suit anyone else - we are all different and have differing needs. However, I do quite a lot of walking - about 800 miles a year - and I'm happy based on previous experience they will see me through 3-4 years worth of walking (or more) between them, so that's about £50 per year on boots.
A £50 cheap pair - even if comfortable - might not actually be any cheaper over time.
Obviously there's no right answer, but I feel happier at getting (to my mind) better quality, more comfortable boots for my money!