Company’s attempt to associate with old Central Mumbai is very expensive (4,1,4)

'very expensive' is the definition.
I don't know anything about this answer so I cannot tell whether this works.

'company's attempt to associate with old central mumbai' is the wordplay.
'company' becomes 'co' (abbreviation).
'attempt to' becomes 'stab' (I've seen this before).
'associate with' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'central' says to take the centre.
The centre of 'mumbai' is 'mb'.
'co'+'stab'+'o'+'mb'='COST A BOMB'

'is' acts as a link.

Can you help me to learn more?