Well from what I've gathered on how you can put TBI on, it wouldn't be that much more expensive. Could even be cheaper. Depends how you do it though. If you managed to get a donor car that had been in a smash then it could be cheap. If you had to fork out for every part needed from a wreckers then it would get expensive.think about how muck pissing around there is doing efi and the cost of efi. there is a lot less with a weber and ya can have it all done and working for under $300. and the difference is huge
How hard it would be would depend on the parts used.
I personally would rather go efi over a weber. That's because I don't like the stalling issue on top of the benefits of efi over carby.
But efi is a little more drastic, webers just the tuning that sounds like a pain.