For you, it might be wrong, but when the advertiser is buying millions of ad impressions and is looking for a 0.01% hit rate, the math shows that you're one of the more likely future customers.
I usually buy a new printer when it runs out of ink because it's cheaper than buying a new ink cartridge.
Also look at third party solutions like external feeds.
Even if it is cheaper, the externalities are not fully priced in, please think of the planet, thanks.
Of course, as you note, printer companies realized people were actually doing this (due to the perverse incentives created by their ridiculous razors/blades business model) so now most printers come with pathetic "starter" ink cartridges that run out after about 10 pages.
The irritating bit though is that many cartridges don't last long (intentionally and unintentionally) once you open/install them, regardless of whether you actually print anything. So, if you don't print a lot, it might still make (financial) sense to buy a new printer... ;-[
I am tempted though to get a model with refillable ink tanks, but most of what little printing I do is on an old b/w laser printer which I've had forever. Still looking for the holy grail color laser printer that is cheap, networked, duplexing, compact, and can print photos.
Relevant ads are the kind you get on DuckDuckGo: relevant to the content you're looking at. E.g. if you look at a site about origami, you get ads from arts&crafts supply stores.
What you've probably meant are called predatory ads: they chase you around the Web wherever you go, like a predator chases its prey.