I'm not sure how eBay reinserted OBO. What was their reason in their email? I haven't noticed that before on any of mine.

They didn't give one. I read the seller boards there for years despite walking away for 10 years. In the last year+ there have been numerous complaints on this happening. They also have them turned on (as I'm sure you know) when listing, hiding it unless you expand the section.

As for shipping, I usually build the cost into my price. If you have bulk lots of stuff, does it help to sell an item in pairs or 3x to combine the shipping cost to squeeze out more profit (as long as a quantity discount doesn't hinder that extra benefit)?

That's what is confusing me. The dimensional weight coupled with the vast increases these last few years (including in the last weeks) on shipping make me wonder how viable many things are for online selling if they are any size or weight at all. I'm waiting to see on the seller boards if the FedEx rates are what is being shown or if many sellers will receive a surprise in their monthly Ebay fees at the end of the month.

I suggest listing some items on Craigslist and Facebook Marketplace for cash as an experiment.

Craigslist was a gold mine in Tucson, but in my current locale not so much. I gave up Fakebook years ago, but will need to create another account soon as I'm wanting to scale to my own website and use venues like Ebay as a funnel (obviously Fakebook as the largest funnel).

I haven't set up Mercari just yet. I will let you know how it goes when I do.

On a side note, can't believe the changes they made to the site here since last night. Evidently there is no more feed from those I follow, so not sure how I will know when anyone posts.