I picked one of these $30 bench-mount cheapies a few years ago, and while it'll hold a bike reasonably well, it's not great (https://www.amazon.com/Conquer-Bench-Mount-Repair-Bicycle/dp/B00KHW8A2Q/). General weaknesses: won't hold the bike solidly in a rotated position, won't clamp well on a seat post, doesn't reach out far enough from the bench to clear pedals consistently. When it dies (whether by use or angry hammer blow), it'll be replaced by a good Park or similar quality clamp.
On the cheap (yeah, I've thought about it), you could build a "euro style" (e.g. Park PRS-20) using a truck-bed fork mount and some scrap metal/wood, mounted to a sturdy tripod or your own leg design (get creative with casters, rotational bearings, etc.). Whether it makes economical sense depends on how much "potentially useful spare stuff" (junk) you've got laying around to work with.
I haven't bought it myself, but was planning to get something like this: amazon.ca
Built a rolling workbench out of two discarded bookshelves, some plywood and locking casters. Then got some plumbing pipe and ran it through the top (with reinforcement), and stuck heavy duty velcro to the foot (flange) so it wouldn't slip out on the industrial carpeting on my shop floor.
For a long time I was using a simple pipe clamp with foam insulation to hold the bikes, but I recently picked up a bench mount set up on Amazon for $35USD and integrated the clamp with my stand using foam tape as a shim.
It swivels, it will hold the bikes at any angle, and since it's mounted to the rolling bench, I can move it anywhere in the shop and still have the bench top work space and bookshelf storage at arms length. I even set it up to take a taller extension to raise the bikes if I'm working on drivetrain or bb stuff for extended periods of time.
All in, I spent about $90USD. A little creativity can go a long way. Cheers!
Here's a photo: https://imgur.com/a/ICp17NO
I've got one of these bench mount bike stands. Works great and allows you to pivot the bike in multiple directions.
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Sorry, put it in the original comment - http://www.amazon.com/Conquer-Bench-Mount-Bicycle-Repair/dp/B00KHW8A2Q/ref=sr_1_2?ie=UTF8&qid=1434768254&sr=8-2&keywords=bench+mount+bike+stand