Actually delosi is the cheapesst (before shipping at least) for liters and I have heard good things about them (but also bad things as with all others).... smaller batches.
But that's the thing about stocking up, usually you gotta go big anyhow, and freeze it, because no telling how long we're gonna be able to buy nic base. I'm not meaning to be chicken little but the fact is in 2024 we lost 4 suppliers of 100mg nic. 1 retailer went out of business (NudeNicotine), 2 stopped retailing nic base (Heartland and LNW) and 1 only retails 24mg max (PerfectVape). So I'd say now more than ever it may be time to actually stock up for however long you intend to vape. The more retailers we lose, the higher prices are probably gonna go before their all gone.