The 24-year-old sealed a £3.75m switch to Upton Park earlier this month, a fee which may rise to £7m depending on a number of clauses in his five-year deal with the Hammers.
Allardyce admits that inflation plays a big role in his recruitment efforts, but insists that Creswell represented value for money.
"Of course, the price was right, which was the biggest factor in our transfer dealings this season. If the player is right and the price is right, we do the deal," he told West Ham's website.
"The biggest stumbling block is the size of the fees that are being asked for today. This one was a very, very good signing indeed, not just for right now but also for the future."