I'm still tapping 500ml bottles of 100mg from Wizard labs and RTS, bought over a year ago. I mix it down to 24mg in small batches to vape as needed, adding very little flavoring ( < 3-5%) to a batch if desired.
Different nic base vendors have slightly different flavors when it comes to unflavored, because unflavored on it's own, isn't exactly "unflavored." There is a slight "peppery" taste/bite to nicotine. Almost like a super light cigarette. So far I've only tried MFS, RTS, and Wizard. I've found that MFS and RTS have a stronger pepper bite to them unflavored, while Wizard is a lot more "clean", which is better for DIY mixing flavors, but not so desirable if I want to vape straight up unflavored. For straight up unflavored vaping, I like MFS and RTS better by far because of their bite. For DIY flavor mixing, I like the Wizard.
All the vendors of nic base pretty much are priced around the same ballpark. I'd recommend you order a smaller bottle from the usual suspects (MFS,Wizard,RTS,Nude) and see which one you like the best on it's own and for DIY flavoring. When you buy 100mg at larger quantities, it's lasts so long it's almost like vaping for free. So saving $10 from one vendor over the other is rather pointless. What you should rather do is see which one's nic base "taste" you like the most, then order the huge bottle of it. You'll forget about nicotine for a long while after that.
Cheers