Why is the first clean more expensive?

On our first visit, we apply a powerful foaming cleaning solution to all frames, sills and doors that gets in to all the nooks and crannies. We allow this to sit for a short while and then use Pure Water with our extendable poles and specially designed brush head to gently but effectively scrub away all the dirt. This dirt is then rinsed away with Pure Water. The extra we charge for the first clean goes toward covering some of the extra time involved in a first clean.