It's kind of comparing apples in oranges. Both are fruits, but they are very different in class of fruit.
If you were referring to TB2, that's a UCAV.
Shahed-136 is a suicide UAV/UAS, single use only.
TB2 would be more cost efficient if used in a scenario where most enemy AD is already degraded to a high degree, giving it high freedom of operation, and you're expecting the odds of losing one is very low. Dropping 2-4 inexpensive bombs per sortie.
But in this high AD environment these class UAVs do not survive for long. Expendable suicide UAVs would be more resourceful at interdiction operations in such environments.
Currently Russian Aviation has to deal with
BUK-M1
NASAMS
Vampire
Gepard
Starstreak & Stingers
And Possibly PACs down the line
Among other EW equipment, tough for a UCAV to survive here for long.