"Il est" or "cest" with "trop serré"?
Are these two sentences correct (where the "il" is an item of clothing such as a coat)?

Il n’est pas trop serré.
Il est beaucoup trop serré pour moi.

I thought that when an adjective (in this case, "serré") was modified (in this case, by "trop" or "beaucoup trop"), you had to use "c'est" instead of "il est."Similarly, are these two sentences correct:

Il était un peu cher.
Avant, c'était moins cher.

Shouldn't it be "c'était" in both cases because the adjective ("cher") is modified (in one case by "un peu" and in the other case by "moins")?

Question

"Il est" or "cest" with "trop serré"?
Are these two sentences correct (where the "il" is an item of clothing such as a coat)?

Il n’est pas trop serré.
Il est beaucoup trop serré pour moi.

I thought that when an adjective (in this case, "serré") was modified (in this case, by "trop" or "beaucoup trop"), you had to use "c'est" instead of "il est."Similarly, are these two sentences correct:

Il était un peu cher.   
Avant, c'était moins cher.

Shouldn't it be "c'était" in both cases because the adjective ("cher") is modified (in one case by  "un peu" and in the other case by "moins")?

Answer

There is a tiny difference. If you say "c'est serré" or "c'est cher" you mean the situation is tight/expensive. It's an impersonal "it". It' not about you and the garment,  It's sort of an objective assessment of the situation without aiming a reproach at anything.

If you say "il est serré" or "il est cher" you are spécifically talking about the garment or the thing. it's now "personal" (as opposed to impersonal). You are pointing a finger at the thing and "accuse" it to be tight or expensive.

Answer

In those cases you can use both, il était or c'était