I can only speak about Air Canada...

If you are traveling from YYZ->NRT on Air Canada and if all if your cards fall right, you could try paying from a last minute upgrade to "Executive First".

If you monitor things closely, you will probably be able to get a Tango (discount economy) for about $1500 (all in)

When you check in you will probably (~75%) be offered the chance to purchase a last minute upgrade (LMU) at the kiosk. Of course other than whether this will be offered, the other variable is the price.

The last two times: once for my wife (who was travelling two weeks prior to me) and once for me, the price was $1298+ (all in). Let's just assume that is the normal price (I have seen lower stated on this board...but they were old posts). The LMU's are available to all fare classes. I know b/c I was on Tango and I was offered and (in a moment of weakness) accepted.

If you took the upgrade both ways that would make it $4100 which I guess breaks your limit.

But if you just want to travel business/F, then you could just take the upgrade on the outbound which would put you at $2800. It sounds like you would like to travel on business/F for the experience. In that case, maybe just one way would be enough. On the way back, hopefully with all the fun you will have in Japan (wonderful country by the way...lived there 3 years myself), you will just zonk out and it doesn't matter where you sit.

A slight word of warning. Air Canada's "Executive First" is half way in-between Business and First. It's better than Business (which I define as wider...longer pitch seats) as they have fully flat beds but by no stretch is it First like you would experience in say at Cathay. But for a NA carrier, I'd say it is closer to First than Business.

As I said, I upgraded to "Executive First" and despite the cost, I was really happy I did it. The food was quite good (get the Japanese main...it is surprisingly good!) and the drinks were flowing. The FA's treat you ALOT better in Executive First. They really work on your schedule whereas in economy (where I am 99% of the time) it's pretty obvious, you have to stick to their schedule).

Last word, if you want to do this all, I would suggest avoiding the three holiday periods in Japan, namely: Golden Week (late Apr->early May), Obon (in August) and New Year's (a few days before and after Jan. 1). People tend to travel during this time which will effect occupancy and thus fares. Besides that, everywhere will be super crowded.

But if you go in say September (wonderful weather at that time)...you should be golden.

Anyway, good luck to you in Japan.

Really a nice country.

PPS. Forgot to mention, if not traveling F back to YYZ, you might want to consider booking a premium seat ($120) on the way back. From experience, I can tell you that sitting in a middle row way back in economy on a 13H flight is not fun.