If you take advantage of zoomania bonuses it's even better. Making a bird out of one of these bad boys is relatively easy, meaning the effective value of this ribcage is more like 343.75E not counting bonuses from secondary skeleton attributes (which can be made quite hefty with 8 skull slots). To be fair we should apply the same logic to the seven-necked ribcage which is worth 68.75 with zoomania. The net profit of this action is thus 37.5E, ignoring zoomania on the thorned ribcage.

Plus it basically turns 225E of amber and enigmas scrippable, which is quite nice.