You gets what you pays for! False economy to go for a cheaper option but accept lower spec. The flimsy hoop diameter means that in a big wind your tunnel can fold up in a twisted heap past resuscitation. If you live somewhere very sheltered which doesn't get wind, or you are getting a tiny 8'x10' model, then fair enough. I live in a windy area where my Northern Polytunnels tunnel (7m x 14m / 21' x 42') has survived 100mph winds. We have all the extras to make it as strong as possible, obviously including the chunky hoops. We also have crop bars which add some stability as well as being useful, plus corner bracers and triangular bracers from the roof ridge down to the sides at each end. The bolts need to be checked after every big wind, especially for the first couple of years.
You can economise by making your own doors and louvres, which is what we did, but I understand that now all doors are aluminium as opposed to wood so probably no advantage to make those.
You could have mesh which rolls down instead of doors but really only practicable in summer, so you would need doors for the winter anyway.
The real cost of a polytunnel is from all the bits and pieces. The frame itself is a fair price, the cover is not too bad, but all the hinges, clips, antihotspottape, louvres, doors and so on multiply the cost up a whole lot.
