I have a few hand held loupes that I use ranging from 7x to 15x. Cost of these have ranged from $10 up to $50. What bothers me most of all of them is the field of view. Because it's very difficult to get edge-to-edge sharpness, every loupe has distortion as you radiate out from the Centre. Some of my Bausch Lomb loupes are very good, but they are very small; roughly 1.5 cm at most.
Amateur photography is one of my other hobbies and I was staring at the macro filters on my desk the other day. So I decided to gang them up to see what would happen. To my surprise, it works great. I think the combination of 10x, 4x, 2x, and 1x works out to an equivalent of 15-20x mag factor (assume it's closer to 17x), and because these filters are 49mm wide, it's very easy to hold, has a wide field of view, and optically very good.
Here's a few pics:
I think my filters are of reasonable quality and total cost was about $100 but there are plenty of cheaper alternatives in the marketplace. For me, I don't have a use for these size filters anymore and they have now found a new purpose.
There is a loupe I considered last year called the "Loupe System", which is advertised to be bigger and better. But at $500-800 (!), WTF!
http://www.loupesystem.com/
But you can buy a similar kit like the one I put together here for roughly $10-20 from eBay. Not sure I'll ever buy a traditional loupe again.