Hmm good question. As sponsor on the forum for car care I think I need to give my input.
It all comes down to individual needs. We all have our own priorities and budget constraints. So what might be essential to me might not be to you. Also what's acceptable to most might not be to the rest.
In my opinion, quality car products do stand head and shoulders above the cheap off the shelf stuff. I'll try to go through a couple of product comparisons to put things into perspective.
Car shampoo
A good shampoo is mild on the paintwork, which means it will not strip any wax protection. (Not only Sunlight strips wax!) It also has a higher lubricity which means it helps your wash mitt to glide over the paint instead of rubbing on it. This is essential when trying to avoid adding swirl marks to your paint. Lastly a quality shampoo has a MUCH high dilution ratio compare to the cheaper stuff. Which means you pay upfront , but the concentrated shampoo will out last its cheaper counterpart. Which doesn't make it that expensive in the end ?
Car polish
Quality car polish gets the job done using the LEAST abbrasive method. Which means it will not damage your paintwork. Also it is MUCH easier to work with. A little goes a long way and it will not dry white onto the paintwork. Also it comes off much easier, which makes the task of polishing much easier. How much is YOUR time worth? In the end you can expect a more cleaner, clearer finish which only compliments a good quality wax.
Car Wax
This is generally where you see the difference the most. Cheap wax goes on thick and dries white. When it comes time to buff, its a mission to remove and you are left with white powdery residue that seems to get into every crevice possible! A good wax, goes on thinly because it spreads so much easier. It dries without turning white and when it comes time to remove, its a pleasure! Most come off with a single swipe ! This makes waxing a pleasure and you actually look FORWARD to waxing! It takes me about 20 minutes to do my car. Oh yeah, lets not forget how much longer a good wax will last. (Provided you compliment it with a good shampoo!)
I have to stress again, it comes down to what works for YOU! If what you are using, works for you then that's all that matters. If not then give the premium selection a try. I haven't spoken to anybody who regrets using quality stuff and wishes to go back to the cheap stuff.
Like I mentioned earlier, quality car care is what I do so it may look like a biased opinion, but I think other fanatics on the forum will agree with me.