Doing an appraisal to arrive at a predetermined value (or value direction ), is an appraiser issue, not a client directed issue. This is stinky of the client and I am not sure they are allowed to do this. But they did it, so if you accept assignment, just know a client this low in their standards might challenge results below 450k.
Also know that with this client is probably a sleaze that gets audited, (and writes targets on orders ), so your appraisal might be challenged in a review at some time. So whatever $ amount MVO you opine, support it well and comment that you reviewed additional sales as well as the comps used in the report.
A statement I often put in appraisals regarding additional sales reviewed : (example)
"The appraiser reviewed other sales in addition to the comps used on the grid. There are properties that sold for higher amounts and properties that sold for lower amounts in the area. The higher priced sales tend to be larger, newer and have a pool or lake view. The lower price sales tend to be smaller, older, and of inferior upgrade houses. The comps on the grid are the more similar to the subject."
A client trying to influence value is what we have here... which is not the same thing as the appraiser shaping their appraisal results come to a pre determined value or value direction . But again, the fact that the client expressed a value they expect adds another level of possible scrutiny to this assignment.