say uncle

Bob's your uncle

No problem, the solution is simple, there you have it, it's that easy, you have what you want, all will be well: indicates a desirable conclusion has been reached with ease.

final say

The right to make a final decision.

have a say

To (receive the opportunity to) voice one's opinion.

I'd say

It is my estimate or opinion.

I'll be a monkey's uncle

Often preceded by well: expressing complete surprise or disbelief.

I'll say

Used to indicate emphatic agreement

let's not and say we did

Indicates that the speaker does not agree with a proposed action, and does not wish to participate.

needless to say

Clearly, obviously.