Cost of installing potlights
That is a tough question. Actually ,with an open attic above--the work is easier than when installing on a first floor,with a second floor above.
Any electrician bidding on the work will have to come to your place and see what challenges await.
Things that affect cost---Your location--Labor is cheaper in Arkansas than in New York city.
Local codes--My area requires conduit--Much more expensive than Romex.
Plaster or drywall?
Will a new circuit from the breaker box be required?
Dimmer switch or regular?
Is drywall or plaster repair(and painting) included in the bid?
If you can answer all of these questions--no one here will be able to give you a guess--Still need to see the job.---Mike---