As indicated above, Vistaprint are great for their deals....
The cost will be in your time... - their interface is very repetitive and finicky.
They insist on upselling everything and anything.
And they will bombard you with a daily email for the rest of your life...!

That said, you can't beat 100 postcards with a cool colurful front for $7 delivered in three weeks. Great for small one-off projects on a limited budget if you have an hour to do it in.

Approximate cost: $50

Quick and simple transaction, Purchased component arrived very quickly with helpful advice for my diy installation.

Approximate cost: $150