OK -- "paddle", not "keyer".
A paddle is either:
. . . "single paddle" or "non-iambic' -- one paddle, that moves left (dah) or right (dit), OR
. . . "dual paddle" or "iambic" -- two independent paddles (one for dit, one for dah) that
. . . . . . can be moved independently.
You can read (in this Forum) endless discussions of which is "best".
You haven't defined "inexpensive". Here's a survey of the low-cost world:
The simplest, cheapest single paddle:
. . . A short piece of hacksaw blade (spring steel), with its end wrapped in electrical tape.
. . . Two contacts (nuts and bolts), one left, one right.
For some examples, see here:http://www.youtube.com/watch?v=ZHvhwFu1aV0
Several world-class high-speed CW sending contests have been won with similar paddles.
With two pieces of hacksaw blade, and a central stop, you can make a dual paddle.
Complexity (and cost) rises from there. Search YouTube for "cw paddle" and you'll get loads of ideas.
I have made (and used) a "paddle" with two "tactile switches" from Radio Shack. It was OK up to about 15 wpm -- dirt cheap, and tiny. I was not the first person to do that, and I don't want to take credit for the idea.http://www.eham.net/articles/13722
You can troll eBay, and pick up a used Bencher BY-2 (dual paddle) for around $60. A Kent dual paddle might be a bit more, but it's more solid in construction. Either of those could be "lifetime" paddles.
K8RA has been making paddles for years. They're reasonably priced (for what they are) and get glowing reviews:http://www.k8ra.com/
Have fun with CW --