Unusual round-trip ticket pricing to Alaska?

Can anyone explain this to me?

A round-trip ticket for May 2023 from Alexandria to Juneau Alaska is over $2200. The same ticket from Alexandria to Anchorage is only $500. Round-trip from anchorage to Juneau is only $380. The numbers are the same for Alexandria to Seattle.

This effectively means that if I book 2 separate flights starting in Alexandria and landing in either Seattle or Anchorage and then book a separate flight to Juneau I can save around $5000 for the small inconvenience of having to spend the night one night in either Anchorage or Seattle. Where is all that money adding up from on a direct flight from Alexandria to Juneau?

Our end destination is Juneau Alaska but we really don’t mind spending a couple of days in Anchorage or Seattle just being a tourist if it means that we can save that much money. I understand that traveling out of a regional airport brings a small premium to the fare but I don’t understand where that large of a difference comes from. Can anyone explain that?