Sometimes when old mowers sell with or without catchers the price difference is negligible, if the vintage mower has a side catcher it can make a noticeable difference to the price.
I've noticed a few people on eBay strip down a restored vintage mower and sell it off in parts because they can make more money that way.
I'm not sure of what the value is for old catchers ,I guess it depends on how desperate the buyer is for the correct catcher but the price is $5 at some tip shops .