Dear Antonio
We cannot directly restrict the cost in the mentioned tcodes using standard. In our scenario , we have followed the below steps to restrict the cost in MB52. Same steps can be followed for MB51 & MM60.
1) MB52 uses the program RM07MLBS. Go to SE38 and create a variant for this program.
2) Press attributes and click on the fields which you want to hide from users. i.e "Do not display values"
3) Set Protect field for " Do not display values"
4) Now create a new tcode for this. Go to SE93 , enter tcode ZMB52 and click on create. Select below option on next screen.
5) Enter the details. Select any of your dev package to save this tcode.
We are done with a new tcode "ZMB52" which can be given to endusers , wherein they will not be able to see cost.
Field is greyed out , so they cannot change it.
Cheers!!
Urvish