You value a point at the cost to acquire, and then at the value to burn. Then divide burn value / cost value to give you your yield.
Hard to value cost to acquire as some may be with no CC surcharge, some with 0.5%-2% CC surcharge. So lots of people use 1c/$ as a rough cost or worse/maximum cost value, as it makes the sums really easy.
In real life, when paying ATO with ANZ Black FF Visa, cost is 0.42% for 0.75, or 0.56c per point which I round down to 0.5c per point as I also have lots of expenses that attract no CC surcharge.
eg. A few years ago I bought my wife a business ticket SYD-LHR return for about 225k points on Singapore + $1.5k taxes. Retail was $8.5k, take off the taxes on both fares and you have 225k points = $7k or about 3c value per point burnt. Cost per point was about 0.5c so got 6x cost value or yield. Or that is how I do it, anyway.
When I do the calcs, I view it as paying a bit more than economy for a business class seat, eg SYD-LHR rtn $1,125+$1,500 = $2,625 v $1,600 for a Qantas economy seat, which is how I justify it to myself - I may be deluded, but I enjoy the almost 50 hours in business for the cost of an extra $1k return, or $20/hour.
Hope this helps.