The salary of a visiting faculty in the university varies. It depends on the cost structuring of the institution. In my experience it ranges from $40-60/hour.
i concur with the salary perception by Maldia as hers and my view are similar w,r,t, cost of living etc.
The visiting faculty are called for (i) when the sourcing university is short of faculty, and on the other hand (ii) when the visiting person is a specialist, and may be filling up the gaps in existing process,
Now bring the economics in: it is demand and supply.
Opportunists and business minded managements would agree with Gilani.
Professional managments too would concur with Gilani.
Intermediates would follow the SOP's laid out for them, depending upon quality parameters. - classifying guest faculty, adjunct faculty and expert lectures