The snorkel on my GX was installed for me, BUT on my first overlander, that was an 1994 F350 crewcab (see below). I wanted a snorkel on it and there are none for those trucks. I did a ton of research looking at pictures and aligning "A" pillars, both from the side for the rake of the snorkel AND how much the snorkel leans in looking at it front on along with it being on the correct side of the vehicle as my trucks air box. I finally found that the 1990's Land Rover Discovery's had the exact same angles and was on the same side as my truck. I had to do this install without an template since the Discovery's template didn't match my trucks lines. But I figured it out and made it happen. It actually came out awesome! Below is a pic of it.
So after all that preamble, the biggest difference will be fitment. A cheap knockoff may use poorly made molds so it may not line up as well with your "A" pillar or when you cut that huge hole in your fender, aligns with the air box. Albeit, if the snorkel is a little tweaked/twisted, it does hard bolt down to the A pillar which isn't a big deal if it's a little off and going into the air box is kind of "pot belly stove" tolerances, so again, there's some wiggle room.
The other issues with a cheaper snorkel is what's all in the box?
You'll absolutely need a template that is accurate. You only get one shot at cutting that hole in your fender.
Best thing I can recommend is check reviews, and most of all be sure there are a lot of reviews, not that you have/need to read them all, but the larger number of reviews for with a higher star rating, the better chances of success. I personally don't believe you have to spend top dollar for a snorkel.
Hope this helps.
My first overlander.