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

I am approached by an agency to run search ads for my Immigration law business. However, I am familiar with Google Ads, and I know that it's going away next year.

My ad spend would be around $1500 and the agency is quoting me a $350-400 setup fee+management, including stuff such as call rail, number pool and management. Is that a fair price?