I used to use cypress mulch for my ball pythons but I have since switched to shredded aspen bedding. It is very affordable and (in my area at least) seem to be very easy to find. If you call around to some local pet feed stores you shouldn't have a problem finding it. I buy 8 cu. ft. compressed bags for $18.99 which I was paying about $8.75 for 2 cu. ft. bags of cypress mulch. As far as humidity goes, my ball pythons are in well ventilated freedom breeder racks so I added a humidifier to the room and the humidity in the cages stays about 65% - 70%.
As for my larger pythons, they are housed in Boaphile cages that have much less ventilation, so with a large water bowl and a light misting every few days, the humidity stays in the 60% - 70% range and these are NOT in the room with the humidifier. I live in Arizona where the humidity this time of year is in the single digits, so I would imagine that in most parts of the country it would be even less of issue.
I also just acquired two Albino Bloods and rather than use the hides I provided, they just burrowed right into the Aspen, which they did not do with the Cypress Mulch. So far the Aspen has been the answer for me. Maybe somebody with more experience has a better suggestion. Good luck!
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