You really won't notice that much of a sound difference - a tech had told me that the "pod" kit or BAK at maximum increased HP by 2.
Most BAK's are around 250. the YA-1906 K&N is 50. For 200 bucks you're getting 2 more HP and a lot more work removing, rerouting and mounting stock wiring etc.
The stock air box has a direct input which leaves the filter exposed - helping suck more air in - it's not a completely closed box. Also - the air box is directly on top of the intake - so there's no chambers or tubing for the air to move through... it just passes from the filter to the intake.
On most bikes the air filter is on the SIDE and therefore needs to travel through tubing of some type before reaching the intake - this is where BAK's help the best - they remove all that tubing to allow the filters to mount directly to the intake - thusly increasing airflow. With the stock box mounted directly on the intake itself - there's no travel time for the air - there is nothing to restrict it - it just passes right through the filter into the intake.
Drilling a few holes in the top of the box to allow more air will get you where you need to be without the extra 200 bucks. I would only think that manufacturers are trying to squeeze a bit of $$ out of people who really haven't checked it out.