No, it’s not possible to set the markup cost for specific item.
But why do you need that?
Normally it should be enough to set the global pricing rules. If for some products you don’t want to apply the global rules, just disable pricing sync for them. I mean it’s possible to turn off pricing sync for specific items. In this case you can to set the prices for them manually and they will not be changed during AliExpress Sync process.