FWIW, I would expect there to be two 'styles' of EGR vacuum valves. Normally open, with no juice applied, and normally closed w/o power.
Apply power, and the valves close and open respectively. The difference in flow depends on the diameter of the hose more than anything else. The electrical connectors would also differ, and that may be the reason for the price difference. I.e., the particular year in question had few failures, so there aren't many on the shelf... price might go up.
I just don't see any other reason off the top of my head for a significant price difference. I don't think there is a lot of 'volume' flow difference, as the vacuum line fittings on most are very similar in diameter. The only place I've seen large diameter vacuum lines are the ones which supply the brake booster...
tom
add: If you can figure out the no/nc of the valve, and do the electrical connection, I'd bet a substitute would work fine.
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