If you search the topic, there is a lot of info on the subject of DIY Tipis.
My take;
There is no real cost savings if you factor in your time. There IS a lot of satisfaction doing it yourself if you are a DIY guy.
Material cost will be from $150-$450 with the various sil fabrics, about $800-$1000 if you use Cuben.
Programs likes Sketchup are fantastic to design your shelter. Once you get it the way you want it you can dimension each panel then add for seam allowance. Save your design to a PDF so you don't lose your design if you discontinue the program [or end free trial period]
Managing the Fabric is a big deal- its slippery. Some guys use glue stick, double stick tape or Pin. Personally I did the pinning....and eventually pinned to start a seam then made lines on my sewing machine table so I could just fold and go without pinning [much faster once you get a feel for it]
You want to use a flat felled seam for it to be waterproof, I just folded twice as it was easier for me to manage seam allowances of all the same dimensions [1 1/4" allowance on mine for a 5/8" seam]
I used a straight seam with no Catenary cut. My reasoning was the other tipis I ve owned and been in lost a lot of useable space with the Cat cut. The cat cut does help tension the fabric better.
If you are doing a Tipi with all of the same dimensions for panels, it gets to where you can just fold and go working your way around in a circle keeping the fabric straight....allowing addl fabric for zipper area of course.
IMHO, its best to sew in your top cone reinforcement during the process instead of waiting
Mine Pictured;
View attachment 82130View attachment 82131View attachment 82132
Montana about 10 miles from Yellowstone, Alaska and in my backyard first pitch.
I did 12 sides as I've seen some of the big paneled pyramid style tipis sag like a mofo. More sewing, and more weight....but stronger with less sag.
I made a skirt on the inside of mine with vents, so I can pitch it a little high and control ventilation.
I have guyouts on mine but have never used them- they haven't been necessary. I've had it in some very strong gusty winds [50 mph] and the wind didn't phase it one bit. The cone shape sheds wind better than any other design I've seen. [I've had winds of 90 mph shred other tents]
If using a stove, keep the pipe at least 12" from your pole...or a tad more.