This discussion is a great example of why it is more ideal to start with mowing residential properties by yourself first. When you do this, you learn bidding basics. You learn how much you need to charge to operate per hour and you don't need a staff to complicate things.
Now that you are in this situation, I want to point a few things out. Don't worry if you are charging too much. If the customer agrees to the price, it's not too much for them. If your bid was too much, they would go with someone else.
Second, we can't tell you what your operating expenses are. That is based on your situation. How much are your expenses per year divided by how many man hours a year are you working. I know you aren't going to be able to answer this at the moment because it is all new.
When you start with smaller properties, you minimize the potential damage you can cause your business by underbidding because it's a small property that won't take too much time and not much in the way of equipment.
When you start with larger properties, you spend more time at the property and need more expensive equipment. If all of this is not paid for by a properly priced bid, it is a lot easier to find yourself not making anything or losing money while working on that property.
With all that said....
I mowed it for cash last 2 months of the summer last year keep in mind I was using a 50in mower. It took me about 8 hours to mow and I could weed eat an blow it in about 6 hrs or less.
So this job has taken you 14 man hours to do.
I bid $2500 per month for mowing twice a month
Let's do some math here.
It takes you 14 man hours per service. Multiply that by 2 mowings per month.
So we are at 28 man hours per month.
$2500 / 28 man hours = $89 per man hour.
If you are making $89 per man hour, I would venture to guess you will be alright with the job.
Now the question is, does this look right to you? Are these hours right?