As a rule of thumb, I consider used tools to be worth about 50%-75% of MSRP, but I have to want something pretty bad to pay 75% of MSRP, at that point I'll just go buy it new from the vendor, LN in this case, and LN is very nice to deal with.
Some cases the item is not available on the LN site, those cases might warrant 75% for me, but common planes I can go buy from LN will be new and if I have any problems they will take care of it. There are no scratches or marks that I might think to myself, "self, the guy did use this, 75% was not such a great deal..."
This is just me and how I think about it, there could be someone else that would be tickled pink that he saved 10%, just that person is not me. While I like LN planes and have several of them, I have a LV plane, and the majority of common planes are Stanley. The LN are easier to adjust and get nice shavings from, but that should never be an excuse for someone with Stanley planes, they work just fine.
If you have a bunch of LN hand planes that you have not used much, you may have let your emotions get the best of you. If you've used them hard and are thinking you can get 75% of MSRP, maybe there is someone around that would do that because they know you.
All that said, one of my favorite hand planes happens to be an LN, it's the 62 low angle jack plane. It has been so useful to me I feel it's worth buying new from LN, they also sell a toothed blade that turns it into a great scrub plane as well as an extra angle blade I believe. $300 list. So I would pay you $225-$255. Even at $225 I don't think I would buy used, and that's the most useful plane I own. I don't consider myself cheap, I have a number of tools I have bought from TLN and he's a great guy to deal with. XLNT customer service, so if someone did buy one and there was a problem he could fix it. The prices for repairs have always been more than fair. This is probably why you were even surprised when you heard it!