You're looking at a negligible performance different from something name brand, and like an 80-90% savings in cost. Moving air into a throttle body is not scientific. Vacuum pressure is vacuum pressure. Removing restrictions is how you improve flow. The filter is the key.

I have an ebay CAI, and I love it. Simple, clean, and exactly like the old-skool AEM, just in 2 pieces. Great fit. The filter isn't huge, and really doesn't need to be. It doesn't restrict anything, and even has a velocity stack cast into the inside rubber. Cost me $32 with shipping with filter, all couplings, hoses and clamps. So, you COULD spend $300 on a name brand and get that extra 1hp, or you could get the function and sound of the CAI for chump change. My bet is that your butt-dyno will never feel the difference that 1hp makes.