Stationary lights no shadow performance

Hi all,

Quick question. I understand that stationary lights with cast shadow on should have no more than 4 overlapping.

If I turn cast shadow off on stationary lights how expensive are they?

For example if I then overlapped 5 stationary lights with cast shadow off is this still a no no for performance? Are they cheap or expensive?

Should I still limit stationary light overlap with cast shadow off to 4?

Thanks!