The input and output pricing per token remains the same between 2.5 and 2.6, although using their image pricing calculator shows a quadrupling of token usage at low and medium quality settings for 2.6. For e.g. at 1024x1024:

2.5 low, 196 tokens, $0.006

2.6 low, 823 tokens, $0.025

2.5 med, 439 tokens, $0.013

2.6 med, 1449 tokens, $0.043

Interestingly, higher quality settings show no change in token usage between the models.