Look this is not rocket science. Salad dressing is one of the easiest things you can make. You just need to remember one rule: 3 parts of oil for each part of vinegar or lemon juice. The rest is up to your imagination. So why are so many people choosing to eat disgusting ready-made crap? I got a free bottle of disgusting fat-free, gummy dressing with my last grocery order. It's going in the trash.
I make my dressing in an empty sake bottle with a tight cap. I just pour my oil and balsamic vinegar in, add some garlic powder, salt, pepper, mustard and give it a shake. Seriously it take 2 minutes.
Why would you pay for a lesser quality product to "save time"? In my opinion, it's not worth it. "But I just made my New Year's resolution to lose weight, I need the fat-free dressing" some people will say. Then just make a creamy one with fat-free sour cream, fresh herbs, a bit of tomato paste, lemon juice... It's so much better, trust me. Just trust your cooking instinct and make your salad happy!