aBroadAbroad

Try your county health department or health care agency. Ours offers a low-cost travel medicine clinic (for county residents only) that runs about 30%-80% less per shot (depending on which immunization) than someplace like CVS (which is already pretty reasonably priced).

A yellow fever immunization costs about $85 per shot, plus a $30 fee per visit per patient. Getting all needed shots at one visit obviously makes this an even better deal, so if yours has a visit-fee, consider getting a Hep-A (if not already done) and see if your kids are due for other regular immunizations (meningitis, pertussis booster, etc.)

I know that's not a lot cheaper than your quote, but there's a very good chance the health department in your county will charge a lot less than mine does, since this is one of the highest cost-of-living areas in the USA.