If LSA ads are converting into Pmax, how much should I pay an agency?

Adding to the ownership thing, also make sure you have admin access on the Google Ads account itself, not just CallRail.

Lead gen Pmax without value based bidding can be a fantastic waste of money as the quality of leads are often god awful and Pmax will keep optimising towards those awful leads. I would hope an agency plans to do a lot more than just set up a Pmax campaign and then boast about how many leads you are getting and how cheap they are. I would be asking for details on how they plan to run an account for you that brings in high intent and well qualified leads.

'I am familiar with Google Ads, and I know that LSA is going away next year' combined with 'If LSA ads are converting into Pmax, how much should I pay' That's an assumption of how the agency are going to run things. You're saying you know about LSA's and you know they're going to become PMAX, so your presumed assumption is that the service you're getting is just LSA, converting to PMAX soon? The issue is, this information should be irrelevant. What service are the providing? It sounds like your expectation is they're just going to type 'immigration lawyer' into a PMAX campaign and not touch it for a year? I've seen what some agencies get away with, and you might be right. Personally I wouldn't just be running LSA, and sure as hell wouldn't be leading with PMAX. Do you have search, demand gen, display ads in the setup? Are they going to ensure all conversions are linked up with your CMS to ensure you know where your best traffic is coming from? Are they going to be reviewing the funnel to ensure landing pages and ads and search terms are aligned and converting the best they can? Are they doing competitor analysis and keyword research to ensure you're on top of your game vs the rest of the market? Are they going to be reporting accurately and in a way that's useful to you? The breakdown of channels and how they perform in terms of leads vs conversions? There is so much that could go into managing an account; and I suppose your idea of fair pricing depends what they'll be offering and where your expectations lie. I've audited clients who have a pmax, never gets touched, and they get a csv file sent to them every 3 months with vague numbers in. And I've charged them the same amount for a service that actually thinks about what their business needs, not just uses a preset template they apply to everyone.

To clarify, what the OP is referring to is LSA getting moved into a custom P-Max campaign type. Ad serving will be similar to before, LSAs at the top of results with call only functionality and a pay per lead fee structure. Also almost no levers to pull.

LSA will convert automatically to 'PMAX' - but will still operate largely the same. You don't really need an agency to manage it as it's pretty hands off. For the peace of mind, it's a fair price. Though it becomes a better deal for you if you can scale your budget up. Just make sure you own the callrail account and have ownership access on everything. Just in case you need to go separate ways.

I would hope an agency would do more than just make a basic PMAX. The fact you're saying that you know Google Ads and trying to tell them their job means most agencies will charge you more. What would you say to a legal client who says you should be cheaper because he knows a little bit of immigration law, and starts giving examples of why your job will be easier soon?

ad spend is $1500 a month or per day? And how much of $350-400 is setup fee and how much is management?

Callrail alone is 55 bucks of that. Just saying.

Honestly, $300-$400 setup fee (does that include management?) sounds too low. You're generally going to get what you pay for with agencies, so if you want good results, it's probably better to avoid agencies under $500/mo, and move to one that is $1,000+/mo asap. Even at $500/mo, you're in the "churn and burn" agency model range where they have to have massive volume to make money, all their help is overseas (nothing wrong with that if they hire well, but few do) and nobody gets enough time.

Ask for a breakdown separating ad spend from management so you see the real margin

That's on the low end for PPC management services, even at your budget. So you are either getting really good value or a provider that's not that good or possibly just starting out. Just FYI, CallRail time is mostly just in the set up (<1 hour typically). Unless something breaks it doesn't need much maintenance. As for LSA, my agency will be adopting it for those clients that want it managed in Google Ads after the transition. But it won't be mandatory; we don't manage it now for clients since there's almost no time involved in it for a retainer. In our case it'll just be slightly higher fees as the ad spend will get added on.