There's a 2023 report to Vancouver city council that breaks down the cost of a scramble, in addition to signal timing changes to add a scramble phase. Not all of these items would be required to convert an existing all-walk intersection to a full all-directions scramble, of course.
- Moving signal poles/heads ($10-100k)
- New signal heads, cabinet, traffic camera ($100k)
- Wiring upgrades ($50k/section)
- Curb ramp with diagonal crossing ($60k)
- Accessible/audible signals (40k for 4 crossing)
- Camera for intersection monitoring ($10-100k)
- Tactile warning strips/pavement markings ($40k)
https://council.vancouver.ca/20231017/documents/r8.pdf
This all-directions scramble here apparently cost them $100k to convert. They've got wider curb cuts, lane painting, new diagonal signals, etc.