Kinda sound like a wanker here, but if I can only by $10k of bonds... that works out to about $500 after taxes in a year. Not a whole heck of a lot, or do they retain the 8% for however long you hold the bond? (e.g., 10 years?) Meaning at 7.2% in 10 years I'd have 20k?
No they have a rate that adjusts to match inflation. So after 10 years you will have exactly the same amount as you started with in real dollars (actually less because of taxes...)
The bonds last up to 30 years, and you can buy the yearly max every year regardless of how much you own. However, they do not have a fixed interest rate. Every 6 months, the rate is set to match inflation.
The interest rate gets changed every 6 months depending on the CPI. The $10k limit is per year - so if you hold on to those bonds you can potentially have $300k invested in total.
As the parent comment stated - this isn't meant to get anyone rich. This is the government providing a service that allows (working-class) individuals to keep a rainy-day fund relatively insulated from risk. If you're able to save more than 10k per year, you're not the primary target for this service.
EDIT: Thanks for the replies. TIL.