"But the 2003 CDC report states that 152,209 people die from mumps annually in the 20th century and 47,745 from rubella."
Table 13-1 which you post a picture of clearly states 'morbidity'. Morbidity refers to the number of cases of illness, 'mortality' means deaths. Table 13-1 states 152,209 per year were sick of mumps annually in the 3 years ahead of the vaccine licensure (not for the full 20th century, the footnote on this is directly at the bottom of the table you copied). It seems you may be confusing some vocabulary.
More broadly, preventing illness is still important. If you look at the measles in the United States this year, there have been 2012 cases, 'only' 3 deaths, but also 227 (11%) hospitalizations (https://www.cdc.gov/measles/data-research/index.html). If we went back to 500k cases a year, that would be 57k hospitalizations a year. Each hospitalization has an average cost of $14k (https://www.cdc.gov/nchs/hus/topics/hospitalization.htm), so this would cost the country about $800M in direct healthcare costs, and then you'd want to add in costs of lost wages for people who were sick, their caretakers, impact of missed schooling, worse care for people who need to wait longer because beds are taken up with measles, etc. to get the broader impact.
"But the 2003 CDC report states that 152,209 people die from mumps annually in the 20th century and 47,745 from rubella."
Table 13-1 which you post a picture of clearly states 'morbidity'. Morbidity refers to the number of cases of illness, 'mortality' means deaths. Table 13-1 states 152,209 per year were sick of mumps annually in the 3 years ahead of the vaccine licensure (not for the full 20th century, the footnote on this is directly at the bottom of the table you copied). It seems you may be confusing some vocabulary.
More broadly, preventing illness is still important. If you look at the measles in the United States this year, there have been 2012 cases, 'only' 3 deaths, but also 227 (11%) hospitalizations (https://www.cdc.gov/measles/data-research/index.html). If we went back to 500k cases a year, that would be 57k hospitalizations a year. Each hospitalization has an average cost of $14k (https://www.cdc.gov/nchs/hus/topics/hospitalization.htm), so this would cost the country about $800M in direct healthcare costs, and then you'd want to add in costs of lost wages for people who were sick, their caretakers, impact of missed schooling, worse care for people who need to wait longer because beds are taken up with measles, etc. to get the broader impact.