Uh. Roundabouts cost orders of magnitude more than stop signs and eat up several times as much space as a standard intersection.
https://safety.fhwa.dot.gov/intersection/innovative/roundabo...
>The average construction cost of roundabouts is estimated at approximately $250,000[2]. Roundabouts discussed in this report ranged in cost from $194,000 to just under $500,000, depending on their size (or "footprint" and right-of-way acquisitions that were needed.)
Let's see... 200k$ roundabout or sub 2k$ (probably sub 1k$) for 4 stop signs installed.