Ultra spec, pm200 and Speedhide(ppg) are equivilant contractor grade paints. BM is the best quality of the three, but PPG is probably the cheapest.
a step up from that is superpaint, Ben from BM, and Pure Performance from PPG. I know Pure Performance Flat is by far, the best of the three cuz its washable. I havent tried the other sheens of Ben, so I cant say. They're basically the same grade though. I get a great deal on Pure Performance, so I use it for everything. Its alt least 10-15$ cheaper per gallon than superpaint, and regal for me, so its a no brainer.
Then there is Emerald, Regal, and Manor Hall. They're all great paints. Im guessing SW is most expensive, then BM, and PPG the least, but I dont know for you.
As far as pricing, you need to shop around. Go to PPG, haggle with the rep after showing your competitors prices. Hopefully they will go lower on all the equivilant paints. Sherwin jacks their prices up due to advertising. They are by far the most expensive for me. I also dont like their paints. If PPG gives you lower prices, revisit the other reps and show them, and try to get them to come down more. Its all about having a good relationship with the paint rep. A good paint rep would rather come down in prices than lose your business. It just turns out that for me, the PPG rep was the only one who gave a chit, so they get my business whenever possible. If I tell him I can get get something cheaper at Home depot, he'll drop the price so I dont go there. Make them afraid you'll use another store if they dont treat you right.