The PE seat gives you maybe 25% more recline than regular economy, with other amenities that are not dramatically different. Then it should cost something like 25% more than regular economy. Not 75-100% more.
I'd benchmark the pricing to floor area rather than recline.
Example the A359 cabin. 38" pitch vs 32" pitch and 8-across vs 9-across means that in the same space (roughly speaking), SQ can put 9x6 = 54 Y seats vs 8x5 = 40 PE seats. In order to get the same revenue/floor area, SQ needs to price PE 35% higher than Y. Add in the champagne, better food, better service (?) etc, perhaps 50-60% price premium over Y could be reasonable?