Do you get what you pay for in Carbide inserts?

I know this is probably a dumb question, and that no one will ever
respect me now for admitting I buy cheap inserts, but----
The question relates to carbide inserts for my lathe and mill.
The situation: I use a 1 1/2" face mill a lot in my old vertical mill
and it has 3 TPG32X (usually 322) inserts. I use several sizes and
shapes of inserts for lathe tooling in my 10" Atlas lathe.
I usually buy inserts when they are on sale at MSC or ENCO, for as
little as $1.50 to $3.00 each, (but always in packages of 10 because I
can't get fewer). For some of the lathe tooling, I can get sale prices,
but some of it never goes on sale.
I can't see the difference in life between the cheap inserts in the
mill and lathe and the more somewhat expensive specialized inserts in
the lathe. What am I missing?
Do I have to buy10 each of the $10 or $15 dollar inserts the get
better life?
Pete Stanaitis
--------------------------