you could go this route, still a bit cheaper than a pro:
http://fast-stairs.com/stair-kit/or, you could go this route:
http://www.decks.com/deckbuilding/Cutting_Stair_Stringersbuilding stairs is, as a buddy of mine put it "where you separate the carpenters from the rest". There's nothing overly difficult if you can work a saw and a framing square, and follow the stringer directions, you can do it yourself. that doesn't mean you should. stairs are something that is either right, or hazardous. for a pro, fairly quick to build, for others, not so much.
i could hire a pro, and he could knock out stairs much faster than i, but i really LIKE building rock solid stairs, even though it takes me way too long.
You'll have to decide for yourself how much your time and the experience are worth to you.