Everything sells when the price is right.
Personally, I think you are asking too much for a pair of small, 2 way 150mm, secondhand speakers with no warranty, especially if you want a quick sale.
First search result shows this:
Sonus Faber Lumina II review
An affordable yet stunning standmount speaker from the Italian mastersTested at £999
I'd reduce them to £450 and put £400 as auto accept on the offers.
The margin on new speakers is high, usually 40%. You're trying to get likely more than dealer cost at £699...
The most I've ever paid for 2nd hand (even perfect in their box as new, current models) is about 40% of current retail. Usually I have paid less than a third (33%). Sometimes way, way less.
Sounds reasonable with that kind of pricing on used speakers. Then it depends on the brand, model and whether they can be sent in a package or not.
People often don't really know what is reasonable. I suspect they don't want, can or have the energy to check what might be a reasonable price. They are just testing. Here is an example:
Monitor Audio Silver RS6:
New, in 2005, they cost around $1100. So what can you get for a pair of 20 year old speakers? You can try selling them for $760:
Here's another ad. Trying to sell a pair of Monitor Audio Silver RS6, during the summer, which is not the best time to sell, for $285. It was on an auction page, with that starting bid. A very well-known place in Sweden, so many people have seen that ad. Although the seller wrote
The speakers are completely flawless and in mint condition. Not sold, not a bid:
By the way, If you say
The speakers are completely flawless and in mint condition and then take a picture where you see a door molding with scraped paint and a dirty wall behind the speaker, it does not give a good impression.
I know the Monitor Audio Silver RS6 goes for around $230 +/- $10 in Sweden. I know because I've been looking at those for a while. Thought it would be fun to try a couple. But then I want to know what the real selling price is. Not some fantasy sums that some sellers imagine they can get.
As you know, if you figure out what the real selling price is, you can buy and sell at roughly the same price and that I think this is the biggest advantage of used speakers. Fun to have different speakers and test them against each other in your living room, listening room. For me, the only way to really evaluate whether I like a speaker is to test it, against others, in my listening room for an extended period of time.