Dell killed off their self-branded printer lines (just checked to confirm), so I wouldn't focus that direction.
I've generally liked the Brother mono printers for light to medium use, but it's hard to know what to suggest without more solid numbers on pages/month. Simplest way I know of to estimate that for small offices is "how much paper do you buy each month, or how often do you buy cases of paper?" Calculating TCO over a number of pages is a pretty simple calculation in a spreadsheet if you have the appropriate starting numbers.
I've attached a spreadsheet PDF of a spreadsheet I did years ago (and abandoned back around 2015) showing some of this, including some conditional formatting to highlight best/good/ok/bleh printers at various page counts. The printer models and prices are all thoroughly outdated and I think there may be a row missing from the conditional formatting, but this may give you an idea. For some of the Brother printers in particular I used the price of a replacement printer as the maintenance kit price, because at 100k pages they'd start complaining about needing the fuser and laser units replaced and the parts simply weren't available. Brother's stance was "ship it to us for servicing and we'll replace them." Riiiiiiiiight.
