You can only have a bubble if ppl pay an ever increasing price for the same good as with the housing bubble and the bitcoin bubble...
this is not the case with AM cause its share price is increasing to reflect the ever increasing value of the company and of the dividends as it is normal.
If AM goes bad the value will drop if they do well the value will raise and that is normal and not a bubble...
If i see ever declining divs or AM doing bad and the price going up then i will start worrying