I never have time to make detailed list and I never get enough good specification from sales/business. Get 5-7 people in the room for planning meeting and try t

I never have time to make detailed list and I never get enough good specification from sales/business. Get 5-7 people in the room for planning meeting and try to do detailed list of tasks. For one hour you can tackle maybe one story or one and a half. I have backlog with 10-15 stories so 10hrs with 5 people is insane amount of money and you cannot do it in one day so it will take two weeks (1hr per day if all people have light schedule). In my experience such approach always ended up with complete disappointment, budget burned on arguments over nonsense.