I buy magnets in bulk at Michael's. They sell in various quantities, sizes and strength. I get a package of 50 that are 3/4-inch diameter ... I don't remember the exact price, but it's something like $8 without a coupon or sale. The downside is the two Michael's stores by me are often out of stock. The only packaging I have on hand says the brand is ProMAG.
They aren't rare earth magnets (or at least aren't labeled as such), but they hold up my dragonflies and several sheets of paper. Everyone I've sold or given them to comments on how strong the magnets are.
I've looked online but haven't found a source with better pricing without having to buy thousands of the darn things at a time, which I'm not currently prepared to do.
I hope that helps! :)
---Aviva