Avoid staying in Monaco. Around is going to cost you since they pretty much all increase prices for the event. In beausoleil you should try Hotel "le Forum". I'd go stay in either Nice ( 20 km ) or Menton ( 5 km ) and get to the race by train. Station is really near the track.
In regards to ticket cost/view of race the best are always in zone K, near the swiming pool and these are pricy. Look on the internet for ticket prices, look on http://acm.mc/gpm/gpm_main.php
Prices on sunday should be from 300 to 500 $. These are for the seats.
Let me know if you need other info, I live there.