This is a
good thread to read to learn about "value".
There was an older thread with the general guideline
$10 in coupons 2 stamps or 3 stamps -- one for the postage; after this every $10 was one more stamp.
Midnighty makes some good points in the thread ... not all $1 coupons are equal. How common are they? What % of the price of the item do they take off - the $1 wub 2 campbells soup = free soup.
My advice is go by
how you feel. If the deal feels good/right to you,then it is. There is a lot of subjectivity with trading.