As the roofer, i wouldn't even consider using
an inferior product, after all i am the one that has to stand behind the product and if you have problems
with the roof later down the line it's me that your going to come to.
Your most important parts of your house is the
foundation and your roof, as a homeowner why
would you waste money on putting 2nds to save a
few bucks now and then have to turn around in
a few years 1-5 and do it again.
I know not everyone has money laying around
and is probably an issue, but your roof is
the last place you want to skimp on, but
it's usually the first place they do.