Indicating degree with 比 and 不如
Can you do the same with 不如?

No, you can't. 不如 means &quot;not as&quot;

&quot;一根香蕉不如一个苹果贵(一元)&quot;
&quot;A banana is not as expensive as an apple (by a dollar)&quot;
It is ungrammatical in either Chinese or English.
&quot;A banana is not as expensive as an apple&quot; doesn't matter it is ten cents less or one dollar less

It has to be &quot;一根香蕉不如一个苹果贵&quot; (A banana is not as expensive as an apple)
When we use [(A) not as (adj) as(B)]. e.g. [(a duck) is not as (heavy) as (a goose)], we cannot make it specific, because a goose can be heavier than a duck by wide range of degree
you cannot put a specific amount/number after &quot;鴨不如鵝重&quot; and say &quot;&quot;鴨不如鵝重30％&quot; ; you can only say &quot;鵝一般來說比鴨重30％&quot; (a goose in general is 30% heavier than a duck)