I had a guy ask me for a quote on washing his house. He said that only small spots, in various spots around the house were dirty. So based on that, he wouldn’t need “the whole thing done”.
I explained to him that the chemical I would need would be reduced, however, the amount of effort would still be the same. I would need to roll my hose out the same way if I was washing three spots on his house, or twenty. I would need to do everything that I would do whether his house was dirty or just dirty in spots. In other words, if it’s only moderately dirty, it still costs me the same to spray chem on your home and rinse it. I asked him if he got ketchup on his shirt, perhaps just the front of it, if the dry cleaner would charge him less because they just had to clean the spot, or if he would need to pay for the whole shirt to be cleaned.
I would figure out your costs - how much does it cost to get you and your equipment at their location. This includes gas (truck and washer), insurance (vehicle and business), chemical costs to do the job, etc.
Determine how long it will take you to do the job (just put a stake in the ground if no experience at all and adjust on subsequent jobs - you could always wash your own house or a friends to measure how long it takes you as a starting point)
Figure out how much per hour you need to make to stay in business and combine that with the number of hours you estimate it will take you.
Add all of this up, do the work, record how long it takes you, rinse and repeat. After you do this a few times, you’ll understand how to structure your pricing.
As others have said, your competitors price doesn’t matter - it doesn’t cost you both the same amount to stay in business and provide your services - you have to figure that out as it applies to you.
Hope this helps. I don’t have as much knowledge as others on here and will always be a student, but I know that the goal has to be to make enough money to be able to eat, pay your bills and continue to be in business. Only you know your situation and can determine how much you need to make to turn a profit. If you don’t charge enough - that’s bad business because you’re operating at a loss. State the price you need to make and if it works for them, great, if it doesn’t find someone it does work for and provide your services to them.
