Yes it is Ok to offer "no extra COST" estimates and embed that cost in overhead.All clients are offered the service at no up front or extra cost customers who are not complete morons will understand that this service is a part of overhead. Telling a customer you are waving a "charge" when in fact you are not is dishonest.
My light bill is also a part of overhead and is embedded in the price I charge when a customer walks into my office looking for a quote I don't tell them that I have a ten dollar "light" charge and I will wave it if the take my bid. Having lights to see by is "free" to the customer.
If the light bill is embedded in the price how is that free to the customer?
Sounds to me the customer is paying for it.
Do you tell the customer they don't pay for the lights, the phone, the office staff, etc. It's all free?
If you give 5 free estimates and get 2 jobs from from the 5 free estimates who pays for the other 3 free estimates?
It sounds like to me the two customers that bought from you not only have to pay for their estimate but also share the cost for the other 3 estimates, yet you told the customer the estimate is free.
Do you tell the customer it's only free if you don't buy from us?