The Guardian could have been giddy with excitement; I think that you are right, but that the Guardian's main point (over-stated, and imprecisely expressed, as even the serious media tends to do nowadays when writing on the fly) that the Brighton squad cost a fraction of what United paid would still be valid (and is what they should have written).
I assume that some of the players may have been home-grown (i.e. Academy products) which, therefore, would have cost the club "nothing" - at least, as far as formally putting them on the books is concerned and for formal accounting purposes when subject to financial oversight.
However, you are probably right, and, while the Guardian's point was more than valid, they could have, and should have, expressed it better.