How much to buy lighting set ,for disney castle?

Hi Suzanne, thank you for your message and for your interest in our light kit for the LEGO Disney Castle.  You can find the product options here:

https://www.brickstuff.com/store/p87/castlelights.html

The final cost depends on the options you pick.  You can purchase the exterior kit only, the interior + exterior kit, and also choose whether to add on fireworks or not.  You can see the various options on the product page above.

Don't forget to add a power supply.  We recommend the USB power cable.

Please let us know if you have any additional questions.  Thank you again!