It can be, certainly. Quite aside from the cost of travelling hundreds or thousands of miles during a re-enactment season, you will need to purchase the costume and equipment appropriate to a person from your chosen historical period. Many clubs Provide "starter kit" for new members, but the vast majority will require you to buy your own eventually.
The actual cost of costume and equipment varies wildly. A Dark Age re-enactor with a basic kit of tunic, spear and shield will probably have spent no more than two hundred pounds in total at the outside (and many manage on far less), whilst a fully-armoured mediaeval knight in plate armour may have spent well over a thousand pounds just on the kit he fights in, let alone assorted sundries. That said, new re-enactors do not ordinarily purchase their equipment all at once - it may take several years for a re-enactor to reach a "fully-authentic" level of equipment because of the expense involved, and many never do unless their clubs require ... more.
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