Only Chelsea winger Christian Atsu and Eibar defender Florian Lejeune have arrived at St James' Park to date and the club's fans are growing increasingly impatient having heard owner Mike Ashley promise his manager "every penny the cub generates" from promotion and players sales to rebuild.
Speaking at the club's 1892 Foundation Cup event, Benitez said: "It's not easy for a lot of teams because the market is a little bit crazy. We have to try to do our best.
"The top sides have a lot of money. The other teams are spending too, but we will see what we can do."
Benitez added: "We know where we are - that is not ideal because everybody wants to see a lot of players signing already, but we have to keep working and see what we can do.
"We can do nothing other than just keep working to find the players that we want, and hopefully we can do it."