Commodity pricing is common to many industries, although legal practitioners seem enthralled by the time-based model of pricing.
Commodity pricing, or fixed-price contracts, provide certainty to the consumer, although the practitioner must assume risk where the actual cost of delivery exceeds the contracted price for the service. The time-based model, which parallels time and materials contracts, places the risk on the consumer, which is probably why it has commanded favour.
Interestingly the Courts have adopted fixed allowances for the costs of certain legal services for the purposes of cost claims.