While people might consider themselves to be doing a "great thing" by re-homing a rescue dog, I don't think it is unreasonable the adoption fees asked for by most rescues. While there is the odd dodgy rescue, most work really hard and generally at a constant "loss" when they re-home.
I have never come accross a rescue that could survive on the donations it receives from it's animals. All have relied on legacies and a massive amount of fund raising by volunteers, whether running charity shops, dog shows, car boot sales etc etc.
A good rescue will neuter, microchip,worm, flea and spend time assessing the dogs character. if it has health issues, it will sort them out where possible. Some even continue to pay vet bills for that animals lifetime if it has a serious ongoing condition.
Even with all the excellent work dog rescues do, thousands of dogs still die in pounds and some rescues every year..the old, the ill, the less cute ones

As always too many dogs being bred, too few lifetime homes...
Just my thoughts
Barbara x