Depends on the country, I know in the U.K. you can buy flat pack stalls which are cheaper and you can assemble yourself
It mainly depends on how nice you want it and the size.
It really just depends. Can be a fairly cheap project or a very expensive project depending on style, location, layout, etc.
it depends how many stalls you want and how "fashionable" you want them, but when you build them you also need to think of the basic essentials like buckets, hay nets, shavings and all those type of things
My step mom and I made a 36 by 12 foot long barn. It has 3 stalls and costed 1000 or less.
The cost may vary depending on how many stalls you want. Do remember that you will have to pay for 1. The arena 2. Fencing 3. Barn supplies such as: rakes, cross ties, shovels , wheelbarrow/ muck bucket, water troughs, hay feeders, and mounting block 4. Alfalfa/ hay 5. Shavings (if you use them). I hope that helped. Just know what your getting into I should know I'm doing the same thing!