Considering that we are such a small percentage of the population to begin with and even then not all of us intend to have surgery, combined with SRS being a one time thing, the cost of covering surgery would be nominal. By comparison, around 50% of the population are able to bear children at some point in their lives and they pay for that.
SRS: Assuming 5% (the actual number is likely a lot lower) of the population had SRS at a cost of $20,000 itemized over 65 years (Birth to Medicare eligibility), that works out to $1.28 per month per person. If the number were closer to 2%, it would be 51 cents per person per month.
Maternity Care: Assuming 50% of the population are able to bear children and 52.4% (as of 2015) will have an average of 1.9 children in their lifetime at a cost of $12,000 to $17,000 per birth, that works out to $7.66 to $10.85 per person per month. That is 6 to 21 times the cost of covering SRS.