There are alot of possible variables. Which part needs to be replaced at $140? Where is the crack in the frame? When the original fix was executed was a reinforcement added along with the weld?
A pic would surely help.
Additionally, when looking to make an extremely strong weld a TIG (Tungsten Inert Gas) weld would be preferable over the typical MIG (Metal Inert Gas) weld done at many shops.
Good luck and feel free to PM with other questions.
'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac