Ama is not 120$, its 30$
GDS will allow you so much more than just the OTAs, look, book, reserve, issue, void & refund.
You can also rebook pax involuntarily in case of IRROP, no need to call stupid hotlines and be stuck for hours.

re com:
You don't get com from the airlines but the GDS, usually you get 1€ / segment.
You get more if you sell a lot.
If you sell enough you'll get access to special rates, called NET / NEG fares. But if you're a beginner I'd rather go through a consolidator who already has access to all these NEG/NET fares and pay them a few $ for each ticket issued and no monthly subscription fee.
You also want to make sure that you chose a consolidator with access to different POS, because like in your example, if you are selling a flight from India, someone with POS India will have better availability in booking classes than you from Switzerland.
If you sell tickets ex U.S., a POS in the U.S. will have MUCH better availability than a POS in Europe.
Starting Q3 2024 many airlines won't be accessible in GDS anymore anways due to NDC, so unless you wish to develop your own NDC access with each airline individually, I'd also recommend to go through a consolidator.