Sounds like a dangerous view of what a S106 is for. The start point should always be what impact does this development have, what opportunities does it offer and what needs to be done to either mitigate the negatives or gain the most from the already identified potentials. Your questions suggest a belief that the development should be seen as an oportunity to raise money. On that basis, although the S106 is adevice outside of the planning system itself, I think any developer presented with a cash sum to pay to make his proposals work, but without any form of development related justification, might well have significant grounds for appeal, should he refuse to pay and the LPA then refuse to approve.
