Rail from La Spezia to Monaco-Monte Carlo?

I think it's not offering fares because it's an international journey. If you make your destination Ventimiglia instead of Monaco, then it does offer fares - €16.10 by regional train, €26.50/34.50 by InterCity, €24.60/35.50 by Eurostar Italia and regional train. Then you can go to www.sncf.com to look for the fare from Ventimille to Monaco (€3.80).