When you have a large hunk of data to send, or anticipate streaming data at a high rate for an extended time, ask the guide for several paths between the source and the destination and send all paths to both ends. AT&T would have called these ‘diverse routes’.
Some classic window-style flow control and error control protocols (X.25 for instance) were adept at exploiting several physical links for a single stream, joining the streams at the destination while preserving the original order to reform the original stream. See multi-flow and error control. With part of the data flowing along each path the code for that protocol can easily observe the extracted toll on each path and quickly optimize their respective flow rates. This adjustment can be done in the span of a couple of network round trips and the error control naturally compensates for lost packets due to the congestion that presumably drove up the price on some of the paths.
This logic is at the end-points. New paths may be acquired from guides during transmission. The guides may indeed pay for congestion and price information that customers can provide at lower cost than the guide’s own testing.
This protocol has the additional social benefit of offloading the overloaded facility very quickly. Neither Tymnet nor Internet has such a scheme, I think. Bit-Torrent does something like this in that data congestion from one supplier decreases the total amount of data that you get from that supplier, without losing any data. Data source location is adjusted according to available bandwidth.
It is not clear how the guide is to choose a set of paths. It could deprecate nodes or links on the paths already offered. It could return a net, perhaps a partial order, instead of a path set. (A partial order is a set of ordered pairs. For every finite partial order there is a unique minimal subset whose transitive closure is the partial order. Oops.
When tracer packets traverse a link with currency change, there is some confusion. For now I would propose that replies would state the exchange rate which would be two numbers which are nearly reciprocals of each other.
The planner needs to know where the congestion is. A price signal could include prices of other priorities, prices at other nodes, even special deals, I suppose. The question is what to propose as an initial standard.
These ideas should be compared with these. There is a common problem of such signals flowing along a circuit without queuing behind extant traffic.