WalMart's in-house brand of diabetes products is called ReliOn, but I think it's mostly just testing supplies (strips, meters, lancets, etc.) and not needles or syringes. I did find BD Ultra-Fine Pen Needles 4mm x 32g 90 count listed for $24.50 but noted as out-of-stock. That's the only pen needle I found on their OTC listings; I don't know if the pharmacy has anything different behind the counter but presumably they do.
When I look up the BD UF nano 8mm x 31g in my insurance, it shows a retail price of $51.40 at about 6 pharmacies in my area (that's all I checked). I'm thinking it's a price set by Becton Dickinson. Presumably your insurance would pay a portion of that price? My insurance pays 100% of diabetic supplies, so I can't get a good read on how much someone else might be charged.
I'd be careful of anything on
Amazon that's shipping from a foreign company. A lot of what I saw there had non-English characters on the box in the picture, so I hate to say but I wouldn't trust it. Amazon Pharmacy lists the product at $54.50. I've never ordered from Amazon Pharmacy so I don't know if your insurance would cover part of that or not.