Yes you are right, but probably this will change when the STEEM value will stop falling, then you can buy SP (I hope). I bought STEEM fore STD yesterday but it takes 3,5 days to get thru, then I can Power up my SP. We I think will just have to wait till this (hopefully) goes over.
But if you own Bitcoins and goes to "Buy STEEM" you can pay with Bitcoins. That's another way. Then using the STEEM to "Power up".