Much much to charge for a private bathroom?

[Jónas Tryggvi Stefánsson]

I'm looking into renting out a bedroom with a private bathroom.

I've done a price comparison and judging by the location, condition and size of the bedroom the ongoing rental rate should be about $840 (rental prices for bedrooms are absurd in my area).

However, that price is not taking into account the private bathroom. Every listing I find on bedrooms, and thereby its prices, is based on a shared bathroom and kitchen with other tenants. 

How much more can I reasonably expect to charge in rent, providing the tenant access to a small private bathroom? At the same time there would not be access to a proper kitchen. 

The bedroom is big enough to support a small functional kitchen area, which will be added (fridge, small stove, microwave) and effectively turning the bedroom into a very small studio apartment.

How much more can I reasonably charge based on this added feature? I've done some searches online and can't seem to find an obvious answer. The room is in an area where not having access to a proper kitchen is not a problem.

Thank you very much in advance! Let me know if more details are needed.