Yes those FX lenses can cost more than the bodies.
My wife made me to an inventory of my camera gear for insurance. Started with the purchase of the D5100 back in 2012 (did not consider my film days adventures with my F90) In those four years between cameras, lenses, bags, lights, tripods and various gadgets I tracked over $10,000 in expenditures. But I do suffer from N.A.S. and indulge my lens lust a little too much. Did not realize just how quickly things can add up. Now that is CDN$ so only $7,500 US greenbacks. There that sounds so much better.
The majority of my lenses are Nikkor but I have several Tamron and have no problem recommended third party lenses. There are some future considerations re guaranteed compatibility but I don't think that is a serious issue.
If you do not have a 'niffty fifty" these are good AND cheap (my AF-D 1.8 was about $100 CDN). The 85mm is about $500 but a great lens to have.
Maybe half my lenses are new, half new to me.
But when buying used it is buyer beware. Almost got burned on a Nikkor 24-70 2.8. Loved that lens - bought it while on a holiday in Calgary. Still paid about $800 so not 'cheap cheap" in my price range but not two grand. Worked like a charm for six days then suddenly it refused to focus. Took it back to the store - it was a consignment so not warrantied by their usual 90 day used warranty. I had not know this. This is where the value of a good store comes into play. We compromised and they gave me a store credit for the total I paid for it. This was "The Camera Store" in Calgary - great place. That used lens morphed into a new Tamron 70-300 (love it) and the lensbaby fisheye - lots of fun, and a monopod. All used lenses I will buy from here on in will have at least a 30 day, if not 90 day warranty, on more costly ones might even go for the extended warranty.
I did buy a used Tamron 17-35mm wide zoom, paid $300 and that included a 3yr warranty from Henry's of Toronto (normally they charge for that but they threw it in free to sweeten the deal). I had gone to look at the new 15-30 which is a much better lens - but a grand more.
I thought I'd like to try a big long zoom - again a grand and then some for them Considered an older 150-500 - still several hundred. Stumbled upon a Tamron 200-400 5.6 while in the States and bought it for $140 (KEH). Got me hooked on shooting long - but watch out, you get the bug and soon you want the latest and greatest - last week I decided this year's tax refund would go to Nikon for their 200-500 5.6. Only 100mm longer than the old Tammy but 20 years newer, +VR, and so much more. Wow what a lens. But $1600 (CDN) and then a 95mm filter adds a couple of hundred more - turned out Nikon's own filter was the best buy - that is rare. And Nikon only gives you a bag to put it in, a case for that one will add another ding in the wallet. Turns out it fit perfectly in a hard body case I had from film days.
Speaking of filters - stopped into a Used Camera store in Edmonton and picked up 3 - 52mm, a 62, and a 67mm clear or UV filters + a used leather pouch to hold them all, for the grand sum of $43 cash (because that's all the cash I had in my wallet and his debit machine was not working). These were HOYA, Tiffen and one Kenko. Looked at each one carefully to make sure no marks. Now only one of my lenses is left naked (should have gotten two 62's

).
I've bought a couple of lenses privately from local camera groups - try before you buy and take your chances. I picked up a AF-D 105 2.8 for $175 which is a steal and it serves me very well.
Used - old - or as I prefer "Vintage Glass" is an option but do you homework and check out the reviews.
I'd buy gadgets and such off of eBay but never glass. Great source of good cheap lens bags though. So much better than the Nikon baggy.
So much depends on what you want to do with it.
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And there is a market place here at Nikonites.