Funny Situation at HND First lounge - Poor me
 

I flew Sun from HND to SFO in Premium Economy full ticket, I saw there was a business empty seat so while in the lounge I went to the counter and asked for any upgrade possibilities.
As I am not JAL member they told me they cannot do with Avios, however they will price it for me.

I went back to my chair to spot planes while having a drink and the JAL member came and her English was not good but her willingness to please and communicate was enough. She wrote in a paper $280 so I handed my Amex and she said I could stay in the seat, she will process and bring back the new boarding pass.
After 10 or 15 mins she is back with same paper and said, it was a mistake and she added one zero at the end of the price, she said; "Sorry I mistake", so price was $2880 for a middle seat in row 10 after my ticket was already pretty expensive, so I declined.

Talking to a friend, she said I should have talked to the manager and asked for the upgrade originally priced, but honestly I did not want to make noise specially to leave in a bad position the JAL employee who missed the amount or exchange rate , so I flew back in a nice Prem Economy seat but not as comfy as the business seat.

Any thoughts? What would you do in my situation?

I believe what you were offered was a change of cabin class by reservation change not a same-day cash upgrade that some airlines offer. I don't think JL does that while they offer cash upgrades from Y to PY.

I wouldn't talk to the manager in your situation since $280 for upgrade to J on a transpacific flight sounds too good to be true even from PY.

JAL does not offer a discounted cash upgrade to J, so what they are offering is indeed as mentioned a repricing of your ticket to the lowest available J bucket. I guess the agent may have made a mistake when calculating from yen to USD. So complaining to a manager would not achieve anything in my best understanding of the situation.

Your friend advised you poorly. It would have done nothing for you and just hurt that poor JAL rep. Lets not be THOSE kind of travelers!

That's not even that bad. I once had to pay an additional 3.5k for a ticket in J that I had already bought 3 months earlier because the gate agent wouldn't let me on the plane with the itinerary I had. I couldn't even argue because time was running down and they had started boarding. Had to call in and they had to forcibly stop boarding on their system so they could book me the same ticket minus a leg to China (I won't go into it). All this because the agent didn't understand some of the loopholes in Chinese visas.

If you are to use loopholes in the Chinese visa, guessing some variant of the TWOV, come in good time, and make sure the check in agent, transfer desk, lounge agent, checks and signs off well in advance of departure. Last time I did a fairly standard TWOV the check in agent came to the lounge 3 times before he was satisfied that all was well.

Since visa compliance is the travellers responsibility be prepared when using unusual constructs. I had full prints of timatic, Chinese visa website, etc ready. Though I never actually needed to go that far.