Is it costly (i.e. roughly how many reads & how much are we charged in $) to have a firestore security like this:
match /profiles/{document=**} {
allow create: if request.auth.uid != null
&& (request.resource.data.firstName is string && resource.data.firstName != request.resource.data.firstName)
&& (request.resource.data.lastName is string && resource.data.firstName != request.resource.data.firstName)
&& (request.resource.data.username is string && resource.data.username != request.resource.data.username)
&& (request.resource.data.email is string && resource.data.email != request.resource.data.email)
}