Honorarium?

What does the bris cost? It's UP TO YOU.

I am a rabbi of a modest-size congregation. Any honorarium from bris milah services significantly helps supplement my "parnassah" (livelihood), and is therefore greatly appreciated. [Cash, Check, or CHASE QuickPay (email: avbillet@gmail.com) - the only way I have setup for credit card honorarium is through the Venmo app]

Taking everything into consideration, Parents will typically offer an honorarium between $360 and $1000.  Average is between $600-$850. [While expenses for multiples (twins, triplets) are the same for travel, the supplies and the additional circumcisions would typically raise the honorarium. Average for twins (altogether) is between $900-$1350]   (See below where expenses are explained in a little more detail)

TRAVELING and SPENDING A NIGHT When I travel (which includes coming for Shabbos), people often give a little more because it typically takes up an entire day, causing me to not take any other bris jobs, and to sometimes miss work as well. Travel is defined by either flying or driving over 75 miles one-way.
Average for a weekday "travel bris" is between $750-$1250 plus travel expenses, 

Average for a Shabbos "travel bris" is between $1000-$1500 plus travel expenses. 

Travel Expenses
* Air travel - plane ticket plus airport parking
* Car rental (+ gas) or taxi/uber
* Driving - about $.50 per mile per U.S. recommended reimbursement
* Hotel accommodations when needed.
Home hospitality for Shabbos is absolutely acceptable at a Shomer Shabbos/Kosher-keeping home. 

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In most cases, "fees" are flexible and could be up for discussion. Beyond what you've read above (because everyone asks me for a "range") I have two blog posts on this topic, the first is more theoretical, and the second is more practical.

A number of factors play into the final honorarium a mohel will receive for his services - details of each follow below.
Expenses - travel, supplies, time
Medical care - he is a trained professional, providing a very important service - in a very delicate area, and he is caring for your son
Ceremony - the style he brings to the service that gives you and your guests the experience you were looking for everyone to have

Expenses - will typically run in the area of $200 (a little more or less depending on how far you live) because you are factoring in the mohel's multiple visits and time on the road getting to you. (Flying a mohel is more expensive as noted above)
Medical care - a hospital can bill an insurance company up to $3000 for a circumcision. Obviously a hospital, with all its equipment and staff, has many more expenses. And if the baby is put under general anesthesia (circs on babies three months and up will do this), we can understand. Most mohels are not physicians and do not take insurance, but the skill involved and care for the baby is worth a few hundred dollars.
Ceremony - is purely subjective. It boils down to what it is worth for you, and what style you prefer. Some people like a grandiose show, some like the mohel to create a mood that eases any tension in the room, some prefer a 'cut to the chase and get it over with' approach, and some like to make it an educational experience. Only you can put a value on the style you prefer.

Your financial situation may also play a role in determining what you can afford.
With the exception of a travel bris when logistics are a little more complicated and more needs to be taken into consideration, we'll typically talk in advance so we are all on the same page in terms of our respective needs for it to work. Otherwise, 

My policy is to accept what you can offer, without questions, and to say "Thank you."