I have a prickly pear mead in progress, so far so good. The recipe was shared with my by someone who lives in NV. No reason why you could not substitute sugar to reach your desired S.G.
Another option is to use your prickly pear jelly--and follow the already documented recipes for "jam/jelly wine" which uses 48 oz of jam/jelly per gallon & typically requires little to NO additional sugar unless you want to kick up the potential ACV.
~3-4 pounds honey
3 qts prickly pear cactus juice (steam juiced)
1-11oz can frozen 100% white grape juice concentrate
water to 1 gallon
1/4 tsp yeast nutrient
1/4 tsp yeast energizer
1 ½ tsp pectic enzyme
Sweet Mead Yeast (or Côte des Blancs, aka Epernay II)
Procedure
Combine juice, concentrate, water, pectic enzyme and sugar to reach desired starting S.G. Cover lightly and allow to rest for 24hr, add yeast nutrient, aerate well and pitch yeast (according to package directions) Ferment at temperature as recommended per the chosen yeast strain.
Dose with yeast energizer when S.G. has dropped by 1/3. Rack from open to air, lightly covered primary to airlocked carboy when S.G. has dropped by 2/3. Overall fermentation of this mead may last anywhere from 3 months to 1 year. Fermentation may stop months before the mead clears. Rack the mead at least once every 60-90 days, as long as dropping sediment. Avoid splashing and aeration of mead during all transfers. Bottle when fermentation is complete and mead is degassed and clear.
When working with prickly pear, it is always recommended to have heat application when processing the fruit (some boil it with water and others steam juice)... even though it sets the pectin in it and causes haze to form in the mead. Prickly pear fruit juice is very mucilaginous and even more so if the juice is not heat processed. The haze eventually settles out. You may dose with equal amounts pectic enzyme when in the primary and as you rack from primary to airlock for the first time. If making a WINE, remember to use your k-meta (or Campden tabs) per winemaking standards.
Of course, when ready to bottle don't forget to dose with k-meta/campden + sorbate if choosing to backsweeten. Always allow to remain under airlock for 7-14 days after stabilizing/backsweetening to monitor for refermentation (per S.G. checks) and then rack one final time before bottling. I recommend filtering prickly pear mead/wine simply because the hairs/barbs on the fruit can be quite minute and are irritating if swallowed.