The one I’m drinking right now is 6.76€ and the cheapest one is 1.28€.
First of all - what a price difference. Secondly, it’s actually not bad. It does have that faint “cheap coffee” taste, but after a few cups I barely notice it anymore.
The real question is: is the tradeoff worth it? Do I give up a few percent of enjoyment on every single cup just to save the equivalent of a month’s grocery bill yearly? I’m not in any dire financial spot - frugality is basically a hobby/lifestyle for me at this point - but it’s getting rarer and rarer to find ways to pocket savings of this level anymore.

In that case you are probably making it the cheapest possible way (excluding some catering grade freeze-dried coffee sold in bin bags) pre-ground is often cheaper than beans due to shipping cost, I take the ~10% increase cost, because I think I can make a self-grind taste at least 10% better. :)
Well, I do have a Moccamaster, which is a pretty decent brewer, but I’m not exactly a coffee snob. I just want a hot, coffee-tasting drink that’s not awful.
If it was just a bit cheaper, I wouldn’t even consider switching - but the price difference is almost five-fold.
Do it, but save the cash (actual coins and notes) and after 3 months, look at what you saved and decided if it’s worth it for you. Great frugal work, whatever you decide.