Ebay is also VERY generous to buyers, if you leave any opening for a return it's entirely possible a buyer will enjoy your item for a few months and then return it at your cost, particularly if they break it or the market value drops significantly, with you picking up the cost of shipping. Even if a buyer orders the wrong part but decides you should pay for shipping to return it, nothing you can about it (even if the buyer admits as much in the eBay messaging system).
Be very careful when you set up your listings, return/refund abuse is rampant with retro computer stuff so I'd suggest making everything "parts-only / as-is" and just indicate how it functioned when it was in your possession.. and make sure you are buying appropriate insurance.
I don't actually think the 15% cut eBay takes is unreasonable compared to other forms of consignment or the much lower prices that Facebook/Craigslist tend to bring unless you are in a relatively populous area. If you are in the US, keep in mind that all income earned via online sales IS reported to the IRS now as part of recent COVID Recovery legislation, so you will want to factor your state and federal tax rates in your overall "cost of selling" math as well.
If you just want stuff gone, use the auction format, the market will figure out what it's worth.