About £400-500 average.
I'm guessing the club are somewhat cautious to not go too big/far too soon just in case we have a bit of a downfall once it is in place. Like Newcastle, Leeds, Sunderland, Villa - massive stadiums in lower divisions isn't the best.
Our owners have always been shrewd but at the same time, don't do things by half so while it may seem small in number, I'm guessing/hoping the actual facilities and quality of it won't be shit.