I hope you bear with me. This is going to be quite a long post. I want to lay out my situation in detail in hopes of getting advice as to what I should do and how to approach it the best way possible.
The situation
I met this client 3 years ago when I was still a student. He hired me as an 'on-call' graphic designer, meaning I would work for them if projects arise. Most of the time I do packaging design—from the label to the box itself. I also handle the final artwork with every material that goes to the printer (which I just learned and am still learning as we go along).
I don't work at their office. I work from home. We talk online. We meet if necessary. I go to their office if I have time (since I have day job). And if I do, I work DIRECTLY and BESIDE him as HE GIVES comments right away.
There was no contract or whatsoever but we verbally agreed I would be paid for every 2-3 projects—which weren't difficult but they require the right creative direction to nail the what he wants—at about $400.
The problem
However, from March to July, I worked on a couple of new projects and old projects for revisions. I was waiting for him to pay me after our last project in July but it was almost September and I still haven't gotten it. I sent him a message telling him about it and even sent him an invoice detailing the projects we did.
He was surprised I was charging him $600 for that time period.
We then met up to settle this time and here's what we agreed on so far. I would give him an amount that I think is reasonable for the work and projects rendered during those months. And now moving forward, we would agree on X money every month if there's a project and X money if there's none. I would send him both figure and see if we could agree on it.
The proposal
I told him $500 for the work rendered in March - July. I said $250/month if we have a project, $80 if there's none.
He didn't say anything about the $500. But he thinks $250 is too high. He told me that I should have a basis for this but I don't know how else I'm going to justify the rate. I based it on the number of hours it takes me to work on a single project — including but not limited to brainstorming, researching, designing, setting up the files correctly, etc.
I then replied him with a range instead. I said that the projects we do usually cost $150-300. And whatever amount we agreed on, I would be charging him $10 per hour on top of the monthly. He will not be charged on months when there's no project.
He said his issue he cannot verify the number of hours I put it. And he wants me to think of another 'formula'.
What now?
I think what I proposed is the best since he will not have to cover any additional cost when there's no project. I think the problem now is that he does not trust me with the number of hours I'm going to charge him for.
What can I do to make sure he trust me with it? Or should I find another 'formula' to charge him for?
Any advice is greatly appreciated.
Location: Philippines.
P.S. Yes the rates are low but they're more or less near the "market rate" for the kind of work I'm doing.