No, the scarcest resource is human time. If person A works for 1 hour then he added 1 hour of human work time to the pool of resources. Therefore it makes sense that he can now extract 1 extra hour of human work time from the pool of resources. Him doing that trade doesn't reduce the number of human work hours available to others, instead he increased the value of the pool since now there is more diversity of jobs the pool is capable of performing.

Your assumption here is that you can trade human work hours for finite natural resources on some market, and that everyone has to pay for those resources on the market. There is nor reason why you should be able to do that, rather the natural system is to allocate all finite resources equally to each person and then you an pay for those with your work, but you working harder to pay a person to share his resources with you wouldn't affect anyone else in the economy unless they too wants to have extra of that resource.