Interesting, for larger contracts the way you bid at Matasano is how mine come out. Scoping engagement, then costs broken down as a guide.
My reading though is what you were doing was still time and materials. Sure you're billing in units of days or weeks, but as I understand it the underlying principle is the same as hourly billing: track time and charge for it. It's not linked to the value of outcomes, it's not eating up unknowns that come out and each has to be negotiated with the client ("We didn't expect $EvilCorp we're integrating with would take 2 weeks to answer every query").
In another comment you say "Time and materials billing does the opposite of keeping everyone on the same side". Can you expand on how you kept people on the same side at Matasano?
> and a clause in the proposal and the SOW that said overages were billed pro-rata additional days.
Did you have an approach that stopped each one becoming a lengthening negotiation with the client over what were true overages and which you should eat? I have had plenty of brusing conversations doing this and in my experience the client's expectation of what's "My fault" can be unreasonably wide, which is one reason for looking to other ways to price.
It absolutely was T&M, but that's not how it's sold. If you read the proposal the way ordinary humans read a proposal, skimming to the price tag, what you'd see is a price breakdown for the whole project, complete with a "total cost" as the bottom row. This isn't some magical thing Matasano came up with; my Matasano partners were from @stake, and the @stake people were previously Cambridge Technology Partners people, and those people were taught how to structure proposals by their forebears before them. Presumably Paul Revere was involved at some point.
We never had any negotiations about overages. If we were going to bill an overage, we'd tell the client, and if they told us "no", the project would presumably have stopped there. It didn't come up.
My reading though is what you were doing was still time and materials. Sure you're billing in units of days or weeks, but as I understand it the underlying principle is the same as hourly billing: track time and charge for it. It's not linked to the value of outcomes, it's not eating up unknowns that come out and each has to be negotiated with the client ("We didn't expect $EvilCorp we're integrating with would take 2 weeks to answer every query").
In another comment you say "Time and materials billing does the opposite of keeping everyone on the same side". Can you expand on how you kept people on the same side at Matasano?
> and a clause in the proposal and the SOW that said overages were billed pro-rata additional days.
Did you have an approach that stopped each one becoming a lengthening negotiation with the client over what were true overages and which you should eat? I have had plenty of brusing conversations doing this and in my experience the client's expectation of what's "My fault" can be unreasonably wide, which is one reason for looking to other ways to price.