You gain no extra Inspiration from breaking down other player made glyphs. Mob Glyphs give slightly more, same with glyphs made by an Alt on your account.
as you get close to the same Inspiration making glyphs as you do breaking them down.
The IP from player Craft-Swapped Glyphs is exactly the same as from an Alt.
And the IP for deconning a glyph from an Alt or another player is a fraction over 90% more than crafting it. This holds across all crafted glyphs until you reach Splendid and Monumental where Splendid drops a little and Monumental reaches over 100%.
The point of craft-swap-decon is that you get both the IP from crafting plus the IP from decon on the same character.
@Nestor
And that link left off without ever actually putting any full table of numbers while several posters were "wondering" about different IP for different glyphs. My tables are current as of this month so I'm going to post them there if you plan on re-linking for new answers.
Before I had even a L50 character, following the tables was the most efficient and wasn't wasting any runes that I wanted for gear.