The James Webb Space Telescope had a $10 dollar price tag, why wasn't it considered too expensive at the time?

Costs increased after it was already under construction so sunk costs kicked in. MSR was still in the planning stages when it was canceled.

MSR was in planning stages *and already* had budget overruns big enough to cancel lunar rover

That cancelled program became famous for leaving behind an already bought launcher that now will fly mass simulator

Sounds quite affordable to me. I'll take a few if you're selling.