1000w lights would pretty much each need their own breaker unless u go 240v. In my opinion 1 220/240v 30 amp breaker would be perfect to control 4 lights with room for a couple fans. The wire guage necessary is readily available, and not terribly over price. I personally like to install a dryer outlet. I highly recommend 4 prong so u can have it safely wired with a mix of 220 and 110 outlets.
To calculate cost, check your electric bill for your kwh price. Keep in mind there is usaually a little bit lower price for night time. I just took an average, mine is about .13/kwh. Google for a kwh calculator there's tons of them. Run your lig cycle during the cheaper time, usually correlates better with temps that way anyhow.
In my experience 9 15 gallon pots well vegged fits perfectly under 4k watts or xxxl hoods. Layouts will vary based on strain, training, light footprint, veg length and other variables.