Boooo! Overcutter! Booooo!
Being serious, happens a lot round my way, someone asks for a price, then say they currently pay £9 for a 4 bed detatched with conservatory...
Some folk are busy fools!
I also come across old plodders with ladders and a rag, who are cheap cos they don't pay tax and are happy to turn over a few bob a week.
Wouldn't worry pal, your pricing sounds reasonable, don't alter that. You are also offering a different service, so you can justify the price difference.