As soon as we didn't meet their proposed schedule and milestones (driven by revenue realization and not technical possibility) mandatory overtime became the rule for the entire team. Of course this was only mildly effective in pulling the schedule back to the left and that effect was only temporary. I believe that we would have been a lot more efficient and likely finished sooner had they allowed the schedule to slip. But the schedule was about revenue and not much else.
We did a lot of stuff stupidly... We shipped hardware before we had the application written (or even prototypes working). We didn't know if we had enough disk space, processing power or network though put to make this beast work. It turned out we needed an additional 20 servers to handle the load we had 5 servers to cover. Tell a Telco that you need another 3 racks, power and wiring in their switch room... Wow what a mess. We integrated and tested our system in front of the customer so they saw it not work for months while we rang out all the software and configuration problems. Why? Because program management advertised that once the hardware was installed, we'd be ready for live traffic, so once it took a phone call, they claimed success (In order to realize revenue of course). Of course it didn't work in production and the customer was upset. During this time I was in a foreign country, working 18 hour days, 7 days a week for months at a time.
As I understand it, once I left they lost that customer who ripped out the system about a year later. I was surprised it lasted that long.
You are right, I think we could have finished with a lot less fuss and cost had we been sensible about things and up front with the customer about what we could and couldn't do. Of course, I'm guessing we would have lost the sale had we been totally honest up front, but we could have delivered a working system had we not shipped the hardware from the factory before we had the software actually functional and we could have integrated things with all hands present in the factory instead of spending hours on conference calls sitting in a switch room with the customer breathing down my neck....