Thought I’d share my experience here since I didn’t find much info when I was looking.
I booked the Norwegian Escape for sail date tomorrow 2/17 about 4 weeks ago and all that was left was interior rooms. I booked the interior guaranteed stateroom in this case. Within a few days I received an offer to bid on an upgrade to a balcony. I placed an initial bid of $155 per person then increased to $205 per person a few days later. I received at the beginning of this week on Monday (we sail tomorrow) an email saying my bid was rejected but they counter offered to an ocean view room for 50PP. I agreed to the counteroffer, but still didn’t see it was accepted. I also as a last ditch effort increased my balcony bid to $245PP. Today I received a confirmation that I won my upgrade bid for a balcony and my card was charged $542. I’m assuming that’s $490 plus taxes and or fees. So ultimately I think it was worth it as that’s still less than had I booked it from the beginning.