Ironically one of my most expensive pipes gurgles the easiest, but I'm not going to hold that against the pipe, it is aesthetically and mechanically perfect for what it is, I just need to find what works best with that design (That would be my Ashton).
The only time I have seen significantly lesser quality is in some $30 pipes from a small manufacturer in Eastern Europe, the tenons were a bit on the loose side (not wobbly, just easier to extract and roughly finished) and the drilling was all over the place (though still functional, just not centered or consistent).
I guess I should note that none of this makes a pipe smoke poorly, it just indicates the potential for problems (a loose tenon may eventually stop holding).
Chances are your cheapest Savinelli is going to be as good as any other.
Basically what you pay for above the $50 mark is fine details, polish/blasting, symmetry, lack of blemishes.
The debate on the preparation of Briar is endless.
That said I did get an Ashton because of what I have read about the way they treat their Briar, whether or not the oil treating has any significant effect on performance is debatable, but at least you know they have done everything imaginable to make the best pipe they can. You still pay for the name but at least in this case a lot of extra work comes with that in regards to the preparation of that pipe.