It depends on the rules of the system. If the system arbitrarily limits the creation of hashcash to 2.5 per minute and limits the total in circulation to 21 M then it could be worth a lot (although with high volatility). Without such limits each unit of hashcash would be worth almost nothing, but the overall system might be more efficient and thus worth more.

Also, if the system limits itself to 7 transactions per second it may not be useful for anti-spam or bandwidth accounting.