It is quite normal to ask for prices and to obtain written estimates detailing all the costs involved.
... These will include the memorial itself with all the required lettering, ornamentation and finishes; its installation on proper foundations at the plot, cemetery or churchyard fees and value added tax.
... (Remember, some of these are set charges which the mason has to pay in advance on your behalf). If you compare prices given by different firms make sure you really are comparing like with like.
.... Are the memorials the same size? Is the stone exactly the same and not just a look-alike? Is the lettering and ornamentation the same and worked by the same method?
.. Have VAT and cemetery or churchyard fees been included?
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What you may choose:
Cemetery and churchyard authorities nearly always have
have regulations, regarding the types of memorials they will accept.
....These regulations vary from place to place and therefore need to be checked
to be checked varieties of stone may be more appropriate in some places than
in others, not only for their appearance but also because of the effect of
or local conditions...
...A reputable memorial mason, will advise you on all this.
It is, of course, possible to choose a design from a mason's catalogue or
display. ..However, if you would prefer something more individual, a
reputable memorial mason will be pleased to design it for you.

Cremation memorials:
...Some cemetery and churchyard authorities may not permit memorials to be erected over cremated remains, and those that do may only permit very small headstones or even just plaques.
... Sometimes there may just be a central memorial commemorating all those whose ashes are buried in that area. Again, a reputable memorial mason will be able to advise on all this.
Your local council office may also help in giving guidance