The price of anything is what two people agree upon, right? So if you pay me 10 dollars to get 9 dollars in 30 years, that means we're betting against eachother

The price of anything is what two people agree upon, right? So if you pay me 10 dollars to get 9 dollars in 30 years, that means we're betting against eachother: you think the economy is going to tank and only losing 1 dollar will be a good deal, which is of course why these bond prices worry people, because in any normal situation you'd expect some positive return on your investment, not just a small loss.