It's a classic case of swings and roundabouts...
If you buy and old, used, cheap cab and get it couriered then yes - the shipping might be as much as the cab itself! But as the value of the item increases, so the relative cost of the shipping gets less!
I shipped an extremely heavy Ampeg head (as heavy as many cabs!) to Eire and it came to less than forty quid, even including enhanced insurance.
At the end of the day, if you want something but can't collect it yourself, then you have to pay someone else. Think of it this way - its still cheaper than driving there and back!