I value them at 350x gems specifically because they are not a 10x summons.
I can save 200x gems by doing 8x 1x summons instead of 1x 10x summons.
Since I usually do 3x to 6x summons per limited time summons, being able to do a 1x summons saves me 900x to 1950x gems per limited times summons.
([Rant, Primer, Summons] 2019 Summons x1 versus x10 - now with Taxi Driver simile)