Welcome to the new USA. Where most businesses are operating at the most they can charge. There is no limit until there are no customers willing to have all their money taken away.
Price Gouging is the new standard. (y)(y)
I bought a 1986, 9.9 and a 1998 30 Evinrude both bought brand new. I have done NO PM on them. Run every day in summer. Since 1986. PM 1 impellor. Thermostat parts in the 9.9. I only run NON E gas, high test, at a marina.
Another reason is with a fully loaded boat. If you suddenly go from Fast on plane speed to neutral ? The motor stalls out unexpectedly. The stern will drop down. And the following wake will run up the back side of the boat. Possibly going into the engine. Causing the very bad hydro / water...
You appear to be showing different manifolds. 1 looks like it is sheet metal riser held together wit just a few tack welds. Do not buy them if they really look like that picture.
I would relocate the bilge pump outlet hose. To a much higher outlet on the transom. Allow for a full load of the boat to determine where the outlet should be. Check valves can stick open. I do the higher outlet hose way.