If you're pushing down hard enough on the edge of the plate to make it rock, it would probably be doing that even without the Sugru pads. Still, I think you could do five or six pads with one 5g Sugru mini pack if you were frugal with it. Mini packs come 8 to a package for $22. Counting shipping, that's around about $3 a plate.
Or, if you planned to do all your dishes at once, you could get the 100g "huge lump of Sugru" for $20 and go as low as $1 a plate. Sugru cures hard within a day of being exposed to air, though, so don't plan on reusing any leftovers.
Sugru is really great stuff. So far I've fixed a really awkward break in an expensive pair of headphones, and repaired and re-waterproofed a pair of shoes whose soles were falling off.