In my quest to find the least-expensive hinges I scoured every builder's catalogue, website, and Chinatown hardware store I could find. The cheapest I came across were online, for about $2.20 for the hinge and $1.20 for the mounting plate. Add tax and delivery and I'm looking at about $4 to $5 per hinge. Meaning 20 hinges would be about a hunnert bucks. Too expensive for me.
Then I found an unexpected source of inexpensive and high-quality hinges: Ikea. Apparently the furniture manufacturer is so prolific that they've gotten Blum, a reputable North-Carolina-based hardware manufacturer, to make them a custom hinge. The unusual design features a screwless cup-mount: You press on a hinged metal plate, and the hinge cup expands tightly into the hole you've drilled in the cabinet door.
The best part is the price: $7 for a 3-pack, including the mounting plates! On Monday I made a visit and paid $53 after tax for 21 hinges, about half of what I'd pay elsewhere. Since you can often get to Ikea for free via shuttle bus (and in New York, a cool water taxi that floats from Manhattan to Brooklyn) there's no delivery charges, just time.
I'll write them up more extensively and tell you if the unusual design works well after I've had a chance to install them.