(1) For a commercial services determination, does the requirement that a market price be "substantiated through competition" mean the current competition (that has not taken place yet) or a previous competition?
(2) Does anyone know, in the world of commercial IT services, what a source "independent of the offerors" might be?
(1) FAR 15.403-1(c)(1)(iii)
tells us that recent prices (i.e., from recent competitions) can be used: "...that the proposed price is reasonable in comparison with current or recent prices for the same or similar items, adjusted to reflect changes in market conditions, economic conditions, quantities, or terms and conditions under contracts that resulted from adequate price competition."
(2) The term "independent of the offerors" means that the contracting officer must use pricing information that wasn't developed by the offeror. This helps to ensure integrity of the information and is part of market research. It would appear that your procurement could be made via GSA schedule contract. Regardless, the price lists in the catalogs at GSA Advantage!
are potential sources of independent pricing information.