Like usual, Launderess raises some good points. It's easy for someone like me to comment that Tide is expensive vs. other brands. But at the same time, I don't have the horror loads that some people have.
I'm repeating myself here, but as I commented earlier, it may be a good idea keeping more than one detergent on hand. Maybe two--a decent value detergent, and Tide. Funnel all the really awful clothes to load that uses Tide. Loads that are more about freshening get the cheap detergent. Whether or not that would make a meaningful cost savings is debatable, however. In my case, imagining that I suddenly had two children (my cousin envies my being childless, and dumps the kids on my doorstep for the summer unannounced, as she heads for a dream European vacation...), I have to think that my approach would save enough money to make my Inner Cheapskate happy. But I am so compulsive about sorting laundry that I'd have many loads that are 100% "light soil". On the other hand, normal people who aim to have as few different loads as possible, would probably find that having just one detergent that does everything the happiest match.