Before anyone says that this is normal or working as intended, please watch the video.
I tried combining the tools you see here in the anvil.
Both of them have a single enchantment and yet it's saying the combination's TOO EXPENSIVE.
I don't think that's normal.
Comments 2
Whoops lol! I should've went with Eff 3 instead of 5! Had no idea I had to do it in that specific order. False alarm my bad! https://www.youtube.com/watch?v=lAViMXCIG-0
Please show how you obtained the pickaxe enchants, e.g. Eff 4 + Eff 4 -> Eff 5. It is normal to be too expensive you started from say, Eff 1, and worked your way up adding 1+1=2, 2+2=3 etc.
However if the pickaxes had been disenchanted via the grindstone and enchanted with a newly obtained (i.e., not multi-combined) enchant, see if MCPE-107211 describes your issue.