Hi,
Do you say keep in mind sth or keep sth in mind ? Yes.
Keep the cost in mind. OK
Keep in mind the cost. OK, probably the more common of the two.
If both are possible, can sth be a clause?
Keep in mind the fact that it is very expensive. OK and common.
Keep in mind that it is very expensive. OK and common.
Keep the fact that it is very expensive in mind. OK, but doesn't sound good if the clause is too long.
Keep that it is very expensive in mind. Less common and doesn't sound good.
Best wishes, Clive