There is no doubt that the land owner has the right to hire a private appraiser and maybe compensated for it. It is the timing that can have a significant affect. The appraisal for an eminent domain case is far different than one for fair-market-value for the sale of the property. There are two very different approaches within an ED appraisal. One is government favored methodology and another being a property owner favored methodology.
If a land owner has an appraisal done before they understand what is being offered and why (best use of property, zoning, severance damages, etc.), they can end up with a premature number (and it may be a low number). That report is discoverable in a court challenge. However, if you wait to receive the jurisdictions offer and report, a low ball number can be argued against. That is the reason to wait.
And just an aside, not all appraisers are created equal when it comes to an ED case. I don't think $1,500 would come close to covering the cost.

