If your account is attached to an affinity dashboard then it does not require a power user subscription even if it is over 1000 nominal entries, however there are certain features like the segmented P&L, CSS customisation etc. that are only enabled with the power user subscription.
If you need to use those features then you’d need a subscription anyway, at which point it doesn’t make sense to link to affinity and have to pay those charges as well. But if the only reason you have a sub is because your account is too large to work without then affinity may work out cheaper.