How to value a Project Manager versus actual Technical/Engineering talent?

I have relatively little experience with recruiting, determining compensation and hiring for startups since this is my first go at it. My approach is that there isn't a single right answer on valuing people. But that said, I am struggling a little bit with something and looking for some input from the wisdom of the crowd. I'm specifically getting stuck on how to value a Project Manager.

I am very much committed to building out a team here that is Agile in as many respects as it can be, and one of the ways I think you achieve that is with talented scrum masters and project managers that respect the developers and their process.

The caveat being that, as a startup with limited cash, I feel very conflicted about how to value the non-developers on my technical team. I'm just not sure how much I'm supposed to value them. I have an equity pool carved out, and my top 2 developers will probably take half of the equity pool reserved for my team. I was thinking of setting aside about 5% of the total technical team pool for a PM, so that would be valued at 1/5th of the equity that the top developers are getting. Furthermore, I wasn't sure whether it made sense to offer the same salary or 85% of what the developers make.

I guess what I'm trying to get at is am I myself underappreciating the role of PM--especially if I'm genuinely committed to doing things Agile? Should I just value the PM the same as the top 2 developers and potentially have to hire one or two less developers as a result?

I'm having trouble valuing the PM higher or on par with the developers, but at the same time, that seems to contradict my fundamental belief that the role they serve towards the developers makes your developers more productive and responsive.

Does anyone have some rules of thumb on how to structure an Agile team from a compensation perspective?

Furthermore, I wasn't sure whether it made sense to offer the same salary or 85%
of what the developers make.

I often wish people would do their homework before asking.

95% of what WHO does? How do you define a developer? This varies widely by knowledge and seniority, the same for a project manager. Want a good or bad one? Normally here you get as good as you can if the project is serious. Noone cares about your cash, but paying 4-5 developers and having bad project management sucks. OTOH the same can be said about developers. Does every developer you pay get the same rate? You indicate so - welcome in a land where the better ones laugh at you and you get the bad ones which think the average rate is better for them than what they get on the market.

Should I just value the PM the same as the top 2 developers and potentially have
to hire one or two less developers as a result?

I think so. Similar to your lead and - if the project justifies it - architect. A PM is very central to the organization, and no, Agile is a lie in that you can not plan sprint to sprint without any bigger picture. In many cases user stories are interlinked and you need to keep all the balls in the air.

In my last project we have 4 different sprints to be aligned along technical boundaries - yes, Agile is supposed that eveyone does the everything. That sadly is shallow the moment you talk of 4 REALLY different technologies (heavy Oracle, BI tool, .NET appplication architecture and a backend with its own propietary programming langauge (OpenLink Endur) which had a 8 weeks release to production red tape everyone must sign it off attitude. Project management was critical to make sure we staged all work along the stack properly.

The PM is really critical - as is the lead developer - to make sure that the stuff worked on make sense and to bypass every stupid little thing that will pop up (ordering stuff, tracking invoices, expenses and all that -not accounting wise, but make sure everything is there when people need it).

Since you don't have a PM, I assume you are managing the process or the devs are self-managing.

Another question to ask is, would it be a better use of your time to focus on other parts of the business? How much equity is worth your time spent on other productive areas? If 10%, don't give PM more than 10%.