If every pair of waders that you have ever bought leak, then you have been very unlucky.....Unless you have only ever brought Simms that is, for at least in the UK every pair leak straight out of the box, perhaps thats why the charge so much.
I fish exclusively for salmon in the UK, and probably average about 2 fishing days a week, so my chesties get more than their fair share of wear and tear. Iv'e tried many makes in my time, and most of them initially hold up well, but with the very best of them, their lifespan, is a maximum 3 seasons.
I have a pair of Vision Extreme waders with a zip, and they are just about to enter into their second season without any problems whatsoever thus far.
I can't say the same for the more expensive Vision Radipor, as I sent back two pairs that both leaked from the very bottom of the zip after around five outings....Was told this was a design fault and the zip was placed too near to the bottom of the crotch area, which put a strain on it every time you walked in them.
The advantages of a zippered pair of waders, if you can find a reliable pair, are well worth the extra cost, not only when it comes to the call of nature, but also with the ease of getting in and out of them, and for a relatively quick and easy addition or subtraction of articles of clothing.