With Trek- Until 1986- the "600" series bikes had a 531 main triangle and depending on year/model- the fork and stays would be made of 501, Mangalloy, Ishiwata... in 86, the lower mid-range bikes got the 531 main triangle with Tange CrMo forks and stays and the mid-mid range bikes got the 531/501 mix.

I'm not exactly sure how it played out for Tenax-

In any case- I think the concept more points to a more stronger bike at the expense of weight than out of price consideration.