I actually have three sets of dado blades.....(don't ask)
I have a 8 piece set of 8" Freud that I bought quite some time ago (10 years or so) for around $80.00 I think but, the price may have increased by now.
I have a 8 piece set of 6" Forrest blades that I bought at an auction for $11.00. (Because no one else knew what they were I guess) they list at over $200.00 now!
AND I have what I would recommend to you. A 2 piece set of Freud box joint blades that I think can be had for around $70.00 new.
I recommend the Freud 2 piece set because they work very well on box joints and you can cut 1/4" joints or 3/8" depending on how you put them on the saw arbor. I probably use them more than the others because they are so easy to sit up and you know exactly how wide the cut is going to be before you even turn on the saw. With the larger sets, not only are they more expensive, you have to fiddle with sorting various blades, chippers and shims then test cut two or three times to get it right.
Now, if you are going to use dado blades for more than box joints only and get into thicker material and wider box joints, I say "GO FOR THE GOLD". "BITE THE BULLET" and get the best set you can afford. You will be happier in the long run and thank me later.
Rog