All of these views are valid. A tree has to be seen for what it can provide. If it’s more valuable to society and nature as a tree, leave it be. If other trees can gain from it being removed earlier than its natural decay demands, I’d argue to remove it.
Trees prevent soil erosion, keep water clean, provide the basis for many beneficial insects and so forth and so on. They have a giant value in our financial system.
I‘d have to get my tables from work. It highly depends on the species, soil, size, location, age, natural area of the species and so forth. A decently sized oak at around 100-150 years old usually gets weighed in at around 2000€. Variation however is a given.