The field guide 'market'
Field guides can pay for themselves most obviously when linked to improvements in performance. Hundreds of pounds can be saved by preventing a single wrong tree being felled and carted to the sawmill, for instance.
Environmental benefits of biodiversity conservation and costs of species loss can be credited to field guides, but it is hard to put a price tag on these functions. Development and research agencies are in the best position to see these potential long term benefits and to support guide production financially. This 'market' has no doubt been a major contrubutor to field guide production in the past. It is increasingly important for this 'sector' that field guides are designed to work by and for the rural poor, and for students in developing countries.
Local Field Guides can be sold for use by, or as souvenirs for, ecotourists. For this aspect, the guides need to be immediately interesting and attractive (hopefully the attraction will grow with greater use as well!).
Many biodiversity 'executives' pay for field guides in effect just to keep them on their shelves like trophies on a wall, as a symbol of domain over the plants therein, rather than because they are actually heavily used . This is the major market for some of the more glamorous field guides. This ' trophy niche' may seem shallow, but helps render a field guide 'functional' from an economic point of view. We are biased to the sorts of guides that are functional from a technical point of view, however.