I see it this way - expense usually means it last longer. I would NEVER spend £1k on an awning - its a bloody tent for christ sake. Yes I expect my £400 awning wont last as long as an Isabella, but I dont care. If the cheaper awning lasts half as long as an Isabella then im still quids in. As long as your cheap awning is dry and thepoles dont bend then so what. Yes cheap often means cutting corners, hence my 'free lunch' statement, and this will likely be the broken zip which will reduce it's life but again so what.
An example is cheap tesco hoovers. We used to spend a fortune on Vax and Dysons, now we buy £30 vacuum cleaners. No they last a third as long as the bigger brands, but for that money I just get a new one. Its a throw away society, no its not Envo friendly, but cheap goods are coming from China (Pyramid!) and they do the job, no quality but functional.