Does not the second film also include the Peel and Castletown districts?
In other words the two films cover the whole Island for the period 1877-1964.

There is also film 0454968 which covers Registered Deaths, Douglas, 1877-1889.
I have not looked at this film but think it gives you the full Death Registration, i.e. it is the material you would get if you request a Death Certificate.

The costs do vary a bit from Centre to Centre. My local centre charges about 50% more, but that may just be a reflection of US/Canada dollar value.