According to academic meta-analyses, the carbon price should be in the range of $100-165 per (metric) tonne of carbon dioxide (equivalents, including other greenhouse gases adjusted for their impacts) emitted. Our World in Data found that about 30% of the world’s emissions are priced, which is up significantly but obviously still low. Uruguay, Sweden, Norway, Finland, Switzerland, and Hungary have charges in this range. The typical price across Western Europe is $65-90. Many countries that have a carbon price charge $10 or less. Still, I imagine getting a legal and administrative system in place is a big hurdle, and once you have one the price can be adjusted over time.