Hmmm, intersesting post and interesting replies.
I've only been fulltime for 7 months so speed is stilll developing.
I quote a job based on the number of days that I think an experienced
tiler will take multiplied by my desired day rate plus materials.
Talk to the customer and give them reasons why they should select you, without being pushy or aggressive.
You take a hit initially, but get plently of work and opportunity to improve your speed.
Good luck