Suggest not to get bogged down with the figures for now. Look at the situation from multiple angles; otherwise, whatever you decide could be lopsided.
You mentioned the training is related to some instruments/products. What are they? More importantly, what's the scope of utility of this training in your long-term career? Would this be useful for you after three years? If yes, it's worth thinking forward. If no, then you should consider dropping it right now and inform your boss that you aren't interested. The downside if you say no could be that you may not be able to stick to this job for long, so better be prepared mentally for this scenario.
Please note that discussing the bond period and/or the amount is something that's not entirely in your hands. Why spend time discussing this over and over again when the chances of these factors being reduced could be bleak? At best, you can ask for a reduced timeline and amount from your boss. However, please be clear that this may also convey a message to your boss that you are not too keen on this and are already planning for the next job. So this step could be dicey too.
Years ago, I got a chance to be trained in power system-related equipment in Germany for 3-4 months with German language training included, with a bond of 5 years or (I think) 2 lakhs [in those days]. I applied what I mentioned above—whether that training would be useful to me in the long term or not. I realized that the equipment was custom-made by Siemens and didn't have many equivalents in those days, so in all probability, I would not only be stuck there after the bond but also this period wouldn't be useful later on (in effect, non-productive from a long-term point of view). I just let it go, and no regrets. It's another matter that I got the US training chance in DAS from Westinghouse within a couple of years or so after that. Maybe I was lucky.
In a nutshell, there's nothing like 'right/wrong' in such situations. It depends on: (1) How the present aligns with your long-term career goals, (2) What's the downside if you say yes now or no now, (3) If you asked for a lower bond timeline and/or amount, how would that be viewed by your boss.
All the best.
Regards,
TS