"I've enquired about three or four players and spoken to their managers and have been quoted wages of £13,000 a week with appearance money on top," he said.
"It's not going to be possible, not with gates of 8,000 - and that's no disrespect to the fans, because they've been great."
Regardless of the club's financial position, Ferguson believes it would be unwise to break their wage structure.
"I don't think we should be bringing in one player on big wages, when everyone else got us to the Championship," he said.
"At the moment, I think we'll be going with what we've got. Our goalkeeper has been good, as were our centre-backs against Palace."
Meanwhile, Posh are seeking a tie-up with Irish side Bohemians with a view to securing young talent from the Republic.
Ferguson has been in Ireland for discussions and took in Bohemians 2-1 defeat by Bray Wanderers.
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