I understand the trade-off is that the re-sharpenable kind will be made of softer steel and so will need to be sharpened several times in the lifetime of one "disposable" saw.
Revise "several times" to "many times". You can sharpen a resharpenable saw as needed for years, decades even, depending entirely on the use to which it is put.
Figure 50 resharpens at minimum and quite likely a lot more if you adopt the little and often practice rather than waiting for the teeth to be quite blunt and then doing a full resharpen.
For me, one of the deciding factors in whether that trade-off is worth it is how difficult the re-sharpening process is.
It's doable, and for most handtool woodworkers shouldn't pose too great a challenge once you commit yourself to doing it (the hard part is starting out). And we are lucky now to live in the Internet age where you can watch and listen to many experienced saw sharpeners doing the work on video and not just have to try to pick it up from books.
That's not to say you can't learn how from books, it's not inherently a complicated process. It's just physically a little challenging, but there are tips and aids that can help with all aspects of it, including teeth spacing and holding a consistent filing angle.
I'd say it's within the grasp of nearly anyone to sharpen a panel saw with rip teeth, most people to sharpen the same saw crosscut. The challenge comes with smaller teeth and the smaller they are the harder it becomes, purely because of the scale of the work.
You will of course need some sort of saw vice if you want to do this, although you can make up something quickly with two boards held in a vice it's better to have a purpose-made tool, whether bought or made. A saw vice raises the work to a more comfortable working height* and is quicker and easier to adjust for longer saws as you work your along the length of the blade in stages.
*If you use two boards in a vice you should definitely sit on a low chair or stool when filing to bring your eyes more in line with the saw file (helps with accuracy and your back will thank you).
As it's the usual hardpoint type, I have read that it can't be re-sharpened, so I have to buy a new one.
This perception is not entirely accurate.
You can, in theory at least, sharpen hardened teeth but because they're so hard there's a risk of fractures or breaking off of tips or whole teeth. However with the right setup (e.g. the right grinding head on an angle grinder) you can buzz away all the hardened teeth and then work with the steel behind them, just as though you were re-toothing a normal saw (this is quite commonly done on old saws if the existing tooth line is heavily damaged by rust, or so irregular from many inept sharpenings that the teeth are unsalvageable).