The costs I was referring to are maintenance over the years. Depending on how much you play them replacing monitors, controllers, deflection boards, isolation transformers etc. etc. worn out from regular use can be expensive, unless you want to ham & egg together non-original pieces or aftermarket parts.
I usually look at the longterm commitment to owning hardware like that, grabbing a working cab in great shape is one thing, keeping it that way is another. It's a big commitment unless your in for the short haul or willing to play them into the ground, and if you don't play them often then it really doesn't matter anyway since you prob won't wear them out.