The Brasserie at the Columbus Hotel (Coulthards gaff) is very nice - I can't accurately remember but it was quite a bit north of £100 for two inc a decent bottle of wine.
Cafe de Paris is over priced but if it's your first time in Monaco worth doing.
The Columbus is distinctly average. Cafe de Paris is over priced but quite an experience. Le grill at the hotel de Paris gets my vote if your budget allows. Need to book and wear a jacket. The terrace will be shut in November which is a shame.