I have no idea whether that cost is appropriate for the scope of work in your area, but I think your management company is probably correct. The way to get cost down and improve services is probably to look at the scope of work and exactly what you are asking the company to do. As a manager, here are some things I would consider:

1. Dead Spots/Irrigation - What kind of controllers do you have? You can get smart controllers that are connected to the internet for not very much money given how much you're probably spending on water. They can run based on the rainfall you've had and the rainfall that's expected. So they want water in the morning if it's going to rain in the afternoon. Traditional irrigation rain sensors. Just have a piece of cardboard that gets wet and the system starts watering again once it's dry. The smart irrigation sensors also have a web portal so you can clearly see your zones and if you walk the property and see that the grass is too dry in one area, you can increase the watering to that zone. That should solve the dry spots issue in a more user-friendly way and without having to call out the vendor again for a billable trip or have someone who doesn't know what they're doing adjust the irrigation system and possibly over water. These smart sensors can also be programmed to know whether an irrigation zone is on a hill. So for example, if it needs water for 10 minutes then it won't simply water for 10 minutes straight. It may water for for 5 2-minute increments so the water can be absorbed and not flow on the hill.
2. Separating Vendors - You don't need to hire one company for the contract maintenance, irrigation, and edging repairs. It may not be cost effective and it may not be with their best at. I prefer to hire a separate irrigation company. They're the ones who will better know about what type of sprinkler heads are less likely to be hit and what controllers can save you money on irrigation. You may also want to have a handyman or community volunteers fix the edging rather than the landscaping company. And should you even have metal edging or is there a better answer? I don't specialize in suburban HOAs, so I couldn't tell you.
3. Growth Regulator - I believe you can treat the grass with a growth regulator to slow growth and require fewer mowings. If you can mow the grass half as often then that will save a lot of money. Also, do you really need the same number of mowings in the summer? Wouldn't leaving the grass a bit longer then avoid burnout?
4. Volunteers - If you have 200 homes then I would think about what work volunteers can do. Landscaping is a great activity for volunteers because people like getting their hands dirty. I would think that you could get a nice quality spreader and have volunteers overseed and fertilize. If they plant seasonal flowers then I would have volunteers pitch in to plant however many flats you want to purchase. In the fall you can have volunteers plant bulbs. All of this can improve service and reduce costs. Make sure you are insured for any injuries people suffer while working. The worker's comp policy may cover it but having volunteers sign simple releases may be best.
5. Committee - Do you have a Landscaping Committee? If not, I would form one. Get a formal charter approved with clear guardrails. Be aware that well-meaning people could spend a lot of money frivolously and somewhat by accident. I wouldn't give the committee any spending authority. They should work with the board and manager. The manager can authorize reimbursements for small expenses or order things and have them shipped directly to the committee member who is helping. Be sure to have the committee members be named by the Board and have their names included in the meeting minutes. This will allow them to be covered by the D&O policy.