there are other companies with competing solutions (PLugPower for sure has 1MW EV charging system). REII's is though the only one that is truly mobile as far as I know.
REII have a great deal to get the fuel cells from GM (let's face it GM aren't selling many themselves so happy to keep production up for REII) and are not doing any complex tight integration with the rest of the BOP needed to drive multiple DC charges. (check the space and racking systems inside their trailer). This means they have high margins since they can use generic parts to do the connections etc. Other competitors will be probably using more expensive Fuel cells (Plug has its own of course) and trying to cram more into the same space which takes more money. Plugs solution isn't just for EV charging but also constant power or backup power for small datacenter sixe buildings so has tech that isnt necessary if just targeting EVs) I am wondering if Bosche are working with Nikola on a similar solution to replace their current Mobile chargers (all battery based). Toyota is other ovolume FC company that may be working with someone if they have excess FC's.