First you have to get big bulky tires delivered to wherever you're going to install them on to your wheel rims. Then you need equipment to remove the old tires from your rims, and install the new ones on the rims. Next you need to balance the tires, then you need to take care of all the TPMS components. After this you need to mount your tires. Forget something? Too bad your car is out of commission til all the above is done.
When I last priced the equipment it wasn't that bad costwise. In my case though it was only worth it to get rid of the whole "dealing with tire shops" issue. A close friend owns a used car dealership and they bought the mounter and balancer. IIRC...it just needed a 240v line.
I have also lost days waiting for tire shops and alignment...as those are the only 2 things I don't do myself.
A tire machine is life changing in a good way if you have a lot of cars you're responsible for. China is starting to make mid-market ones (simple pneumatic ones that are powered bug geared to home use rather than professional like the ~$1k electric machines) for ~$400ish that I'd take seriously if I was in the market
Once you have a tire machine you'll spend more time at the tire shop (outside business hours, lol) because their trash pile will be your best source for reasonably new used tires. They sell a lot of sets of 4 when 2 would do.
definitely not easy by yourself, but the whole process (change, then alignment etc) shouldn't take a decent mechanic's shop more than a couple of hours. I've changed tires on my nearly 200k mile car several times now, and it's usually a few days for the tires to be delivered (in america the mechanic will just receive it) and a 2h appt to get the work done. I'm shocked your parent comment mentioned waiting a whole day at the mechanics'.
My friend does this at Costco, and it takes longer purely because of appt mismanagement and backup, the work itself is quick.