While this question can easily be answered by spending a few minutes actually shopping for a gi - especially here, at the Fighters Market website, where we have some handy dandy price filters - I'll go ahead and humor the idea... as well as raise you a few insights on cost versus value.
The vast majority of gis range from approximately $70-$90 for a simple, basic gi to approximately $160-$180 for a fancier and/or more durable gi. Of course, you can always find those off-brand jiu jitsu gis sold on Amazon for much less, but you have to keep in mind that "you get what you pay for". That doesn't mean that all basic gis aren't worth buying. I actually wrote a blog, "Battle of the Basics: BJJ Gi Comparison", about those basic gis that we felt were definitely exceeded their worth. Since then, other gi brands - such as Maeda Brand with their Red Label Gi and Progress with their Foundation Kimono - have really stepped up their basic gi game.
So what makes a BJJ gi worth more? More often than not it's the quality of materials and construction. A jiu jitsu gi that costs more should - we would hope, anyway - last much longer than a cheaper gi. The fabric is typically a thicker or tighter weave, or is a brand new weave technology that might be lighter but is designed to withstand greater stress, or the attention to detail and care taken during construction is on a different level. Sometimes the extra cost is directed into the aesthetic elements of the gi, such as an illustrated interior jacket lining, or fancy patching and embroidery work. These latter increase the cost of labor for each and every piece made. Then, of course, there are some gi companies that can charge $200+ for their gis... but the "higher value" is usually thanks to clever branding and marketing ploys rather than any real inherent worth.
So, how much should YOU pay for a gi?
That's really all relative to your budget and preference. If you're just starting jiu jitsu and you're an average Joe, I would suggest starting with a single basic gi until you decide that you're really going to stick with it. Once you're hooked, you'll quickly find that you'll need at least three or four gis to get you through the week. At that point, you might consider investing in a couple slightly higher quality gis, as well as a nice fancy gi that you can go compete in. If you're just starting jiu jitsu and you're the type of guy or gal who likes to show off his/her success... go crazy. Just please, make sure that whatever you buy, it fits and makes you feel like a boss. Here's a little guide on how to do that.
See you on the mats.. Oss.