I agree that $80 is a good price, provided that it has a bobbin case and that it doesn't need new power cords/foot control. If it's missing the bobbin case, that will cost about $32 to replace, and the cords and foot control a little more.
If you search for Touch & Sew attachment sets on eBay, you can usually buy them for a lot less than sets sold specifically for the 301, which is somewhat "collectible" in that quilters and seamstresses really love them.
If you want to buy a buttonholer for it, you will want the old-style type that was originally sold in the maroon colored plastic "treasure box," not the green or the black boxes of the same rectangular shape. Those were made to be used with the straight-stitch on a slant-needle machine. A later style buttonholer was sold in a pink (for slant) or an aqua (for vertical) "Jetsons" box - oval and very retro looking.
I had a cabinet like this one and I liked it a lot - kind of Shaker style.