Cost of stationary lights without shadows

Is the rendering cost of non-shadow-casting lights the same as those that cast shadows? I was thinking of positioning some faint point lights over decals in my level to make them show, because they don’t really show that well under indirect light. However, if I add numerous lights this way, how much hit would the performance take? I’m turning off shadow casting for all of them.

Non shadow casting lights are considerably cheaper. The performance of such lights is mostly dependent on the number of pixels they affect on screen.