The Medisave claim for a colonoscopy is between $950 and $1,250 depending on whether you have other procedures performed in the same sitting. This is applicable whether the scope is performed in a public institution or in the private sector.
Different institutions, centres and endoscopists charge different amounts for the procedure depending on various factors such as rental, equipment and manpower costs.
You can find more details on the pricing of colonoscopies in Singapore in the Complete Guide To Colonoscopies In Singapore (2018).
Alternative, you can call the various centres of interest and enquire about colonoscopy prices prior to making a decision. Remember that the pricing will change if there is a polypectomy/biopsy performed during the procedure.