When you factor in compounding and triple tax advantages (contribution/growth/withdrawals are tax exempt), it can be quite a lot of money over 20-30 years. HSAs can be invested as well say in a target fund or index which should net 5-10% per year. Like a 401k, contributions also lower your taxable income so they save you from taxes today.

Try it yourself:

https://www.hsabank.com/hsabank/Learning-Center/HSA-Savings-...