Main cost driver is the price of green hydrogen. It is already cheaper than the natural gas prices we are paying now (equivalent of about $1700 per 1000cm of natural gas equivalent vs about $2500 we pay), by 2030 it should be down to $500 per 1000cm natural gas equivalent and that's about 2019 price.
Production costs are easily low enough to go further and faster than that. Logistics and economics may slow things down, but it’s not a cost problem right now.
Yes and no. For raw energy production, it is dirt cheap. Storage and transformation is a bitch though, and so far costs are quite high there although they are getting better. Given that we will need to increase green hydrogen production by 400x in 9 years and further 4x in next 20 years, prices will of course drop.
Hydrogen is the easy one. If you want battery storage I agree we need to get it cheaper (the effective cost of battery storage was close to nuclear last I checked, which isn't cheap enough, though my numbers may be out of date), but hydrogen is something I first made when I was single-digit years old.