How many pages/year is "lots"?
Will you be buying only OEM cartridges, or aftermarket carts, or DIY bulk toner refills?
While a monochrome laser is the way to go for cheapest cost/page, the answers to the above two questions matter a lot. For example it is still fairly expensive (for a B&W laser) to get the HL-L2350DW but then get the 3K page, $75 OEM carts which don't even have the drum built-in, is another $100 per 12K page rating.
On the other hand if it would take you a few years to print 3K pages, it could be a false economy to make a larger initial investment to get something that takes 6K+ page carts and longer lasting drums.
If you don't need highest print quality you can stretch drum use out and also gamble on 3rd party carts, but the cheapest way to go is get bulk toner then chips or reset gears, etc (depends on what the particular model needs) to DIY refill them.
Depends on how hands-on you want to be. Some are refilled by just pulling a plug. Some need a hole cut or melted in then a refill kit includes a plug. Some need an access panel removed by drilling out plastic-welded studs to access the plug then the panel may need screws added to put back on.
Cost difference depends on how many drums you go through, but ignoring drum (and paper) cost, $75 for 3K pages OEM cart equals $0.025/page, while bulk toner (taking first random example I saw), $12 for a 2 pack of toner refills, so 6K pages is $0.002/page, less than 1/10th the cost. Aftermarket carts fall in the middle, or about 2-3X the cost of the bulk toner but the quality can be spotty so buy from a place with good customer service. I would not get aftermarket drums, they tend to make lighter print and wear out faster.
Another option is a larger, used monochrome laser. Brother would again be a fair choice. You can probably find a mid-sized unit for $100 that still has 200K pages worth of life left, and takes 6K page or higher carts, but if you want modern OS driver support, be sure to check on that before purchase. With only printing, not AIO features, the drivers built into windows may be enough by themselves but the OS has to have them if the printer manufacturer has stopped releasing new drivers with each new (Windows) OS version!