Exceeding annual allowance HRT payer and child benefit

Mistermeaner

Potential eureka moment - please check my thinking 

Exceeding the annual allowance means paying tax on the excess at your marginal rate 

So for a HRT payer 40% on anything greater than 40k (Assuming gets full allowance)

So in general it's not worth paying more than 40k in as your nett no wealthier but have just tied up your cash (and pay tax on it again when withdrawing potentially )

However if one has 4 kids and claims child benefit it must all be paid back if earnings are over 60k 
In this scenario might it be beneficial to pay extra into pension exceeding the annual allowance in order to stay under the child benefit charge 

E.g. Someone earning 100k:

Pay 40k into pension , gross pay 60k lose all child benefit and pay 40% tax on 10k 
Or
Pay 50k into pension, gross pay 50k keep all child benefit but pay 40% tax on 10k for exceeding AA 

TVAS

£3,720.80 child benefit for 4 kids versus 4k tax exceeding the annual allowance.