Well as the site says the cost of the collection is considerably cheap to what it might actually sell for piece by piece. A Sierra collection would still be huge but it would be comparatively smaller and more manageable, so any collector selling such a collection would likely seek closer to selling value for each item.
I have a stack of old computers in my room waiting for me to take them apart and put them into working order for running Sierra games 🙂 My parents see the stack and do think I’m insane 🙂