For the purpose of “buying” points I value it at around 1.5c per point, this seems to be where I've landed given mix of redemptions, availability when I want/need comparable competitor fares, and whether I would actually pay the value for premium cabin (example SIN-MEL return is 116,000 pts .. at 2c per point = $2320 + taxes ~ $2450 . Undoubtedly good value, but probably wouldn't pay that myself.
As for "buying" points, in a different position to most, but there are several ways I can legitimately "buy" points without literally buying points ...
- paying for anything in Australia on my SG issued visa, instead of AU Amex, I earn 2.4 pts/$, so that is effectively buying points after accounting for net FX fees (in our case Visa FX fees - the fee we pay to transfer money to Australia) and merchant imposed fees for the different payment types.
- offers that allow you to earn extra points on credit card by paying extra fee (eg an offer for paying 2.2% fee to earn extra mile per $ .. no thanks)
- forgoing annual fee waiver on credit card for 10,000 bonus miles
- Paying more for airfares that earn more points
- etc