I am not sure where to place this question, so I am asking it in this section.

Let's look at U.S. 20+ year Treasury bonds. Most of them are trading above par value of 100 (102-109 range) with some as high as 132(e.g. T-TIPS 15-Apr-2032). This is 32% over the guaranteed value of the bond - an investor who bought it for 132 will only get 100 at maturity - a sure loss.

The interest on the bond is 3.375% (nominal), so the best an investor can get is 3.375/year * 30 = 101.35 in interest over 30 years. that would double the par value but with 32% premium it is only 69% or 2.5%/year. The real return is probably already below zero if we factor inflation in.

With that math in mind, what would a highest possible price of bond be ? Is it par value plus all interest paid till maturity (100+101.35=201.35 in this example)? Does it mean bond funds like TLT can go up another 50% or so?

Thanks