How my $69 air duct cleaning coupon turned into a $500 event...

I've been wanting to get our air ducts cleaned since we moved into this home. I was in doubt that they had ever been cleaned. Flipping through some coupons, I found a deal for a $69 cleaning. I called, made the appt. and they came out to the house today. They started cleaning our air ducts and found MOLD -- yuck!!! We've been breathing this nasty junk in for sometime now... Anyway, it ended up costing $500 to have it all taken care of. I did manage to get the ducts cleaned for the $500 cost though!