You can retire in many places for significantly less than what it would cost in the US.
As an example, the average wage of a professional white collar worker in Vietnam is ~$450 per month.
Banking: 7.6 million VND/month
Pharmacy: 7 million VND/month
Food Industry: 2.3 million VND/month
Western English Teacher: $1000-$3000 (varies a considerable degree, depending on who you ask)