Talk about the good old days

Let me create a cost if you bought two gameboy advances, a link cable, Pokemon Box, Pokemon Colliseums/XD, and all five gen III games:
Gameboy Advance: 99.99$ for the original mode, 79.99$ for later models (SP) (186.44$-149.15$ accounting for inflation)
Pokemon Ruby/Sapphire/Fire Red/Leaf Green/Emerald: 34.99$ retail (65.24$ accounting for inflation)
Link cable: 14.95$ (27.88$ accounting for inflation)
Total costs for two Gameboy Advance SP's, all five games, and a link cable: 79.99 x 2 + 34.99 x 5 + 14.95 = 349.88$ (652.37$ accounting for inflation)

Now might as well do the same thing but just for Legends Z-A, same local thing with two consoles:
Switch 2: 449.99$
Pokemon Legends Z-A (Switch 2 Edition): 69.99$
Total cost for two Switch 2's and two copies of Legends Z-A: 1039.96$

So in summary for a similar modern setup within the same generation (and only with games that can trade between themselves) the GameBoy Advance setup would still be cheaper if you bought a completely offline setup to trade with Gen III entirely than to buy an offline setup to only trade with Legends Z-A, and this is to get the complete experience. Sure you can use Pokemon Home to help with some Pokemon transfer and storage but that still does not solve Pokemon that need to be traded, either you go online or you get a second console. Let me also get the cost of having a single Switch 2, Pokemon Legends Z-A, and a Switch Online subscription:
Switch 2: 449.99$
Pokemon Legends Z-A (Switch 2 Edition): 69.99$
Nintendo Switch Online: 3.99$ for a month and 19.99$ for a year
Total cost if you went for a month: 523.97$
Total cost of you went for a year: 539.97$

This is cheaper than the complete offline setup for the GameBoy Advance, but that isn't really much of a fair comparison since one is meant to be fully offline. Might as well make an equivalent for the GameBoy Advance assuming you trade with others eliminating the need for two consoles:
Gameboy Advance: 99.99$ for the original mode, 79.99$ for later models (SP) (186.44$-149.15$ accounting for inflation)
Pokemon Ruby/Sapphire/Fire Red/Leaf Green/Emerald: 34.99$ retail (65.24$ accounting for inflation)
Link cable: 14.95$ (27.88$ accounting for inflation)
Total cost for each game but only a single console (SP): 204.85$ (381.95$ accounting for inflation)

The GameBoy Advance in-person setup is cheaper than the online Switch 2 setup, and just for fun might as well make the giga-offline setup plus the GameCube and games:
Offline GameBoy Advance Setup: 349.88$ (652.37$ accounting for inflation)
GameCube: 199.99$ (372.89$ accounting for inflation)
GameBoy Player: 49.99$ (93.21$ accounting for inflation)
Pokemon Colliseum/XD: 49.99$ (93.21$ accounting for inflation)
Pokemon Box R/S: 19.99$ (37.27$ accounting for inflation)
Total cost: 669.84$ (1248.95$ accounting for inflation)

Sure the giga-GameBoy Advance pokemon setup for every single Gen III entry is more expensive than the Switch 2 offline setup for A SINGLE GAME but its still funny how the complete GameBoy Advance setup is still cheaper with inflation than the Switch 2 offline setup for a single game (this would probably be a similar price for Winds/Waves). I bet that if I did a similar setup for the Switch it would be much more expensive for every Switch Pokemon Title and Pokemon Home, but that is for another time.

I am assuming that it is already paid prior as an essential service.

Nope. Some of us survive with the minimal ISP as possible.