Field Trips / Outings - do parents pay extra for this?

For those of you who take your daycare kids on field trips/outings to places that require admission fees, etc...do you ask the parents to cover this, or is it something you take into consideration when setting your daily rate and you pay for it? Are there certain trips that you pay for, and others you ask the parents to pay for? I'd like to see what everyone else does.

I factor all field trips into my fees - I do my best to find FREE options low cost - they are a write off anyway and something I offer for ME as much as my crew cause change of a scenery helps us all!