Fees for lap infant on international flight booked with UR
 

I'm looking to buy a flight from Los Angeles to Mexico City for my wife and I and our 1-year-old (as a lap infant). I was surprised how low the cost for our daughter was when pricing it using UR points.

The breakdown per adult ticket is $315 for the fare, and $149 for taxes and fees. The total amount that Chase seems to be charging for our daughter is $16.85 for taxes and fees (and $0 for fare). Can that be correct? I expected the fare to be 10% of ours (so $31.50), and to pay the full taxes & fees, for a total of $180.50. Am I wrong about that?


If I were to book this and I am in fact being undercharged, am I setting myself up for any issues at check-in time, at the airport, or (worse) upon landing in Mexico?



Thanks!

You may receive more helpful responses if you mention the name of the airline.