'on a contingent deferred basis' = the CONTINGENT basis on which the DEFERRED sales charge will be paid. Hence my translation, which doesn't imagine/make up/speculate some "future sales value" (valeur de vente) when the sentence is reading "deferred sales charge" (frais de vente différés).
Definition of sales value: the amount of money which would be received if something is sold.
https://www.google.ca/webhp?sourceid=chrome-instant&ion=1&es...frais de vente différés : les frais - définis aujourd'hui - qui vous seront facturés plus tard.
frais de vente futurs : les frais qui seront appliqués dans l'avenir.