Messi currently makes 50m annually, which is 100m gross.
The same salary at Inter with the new tax gives out a cost that is closer to 70m. [forgot the new tax figures]. Doesn't mean that he won't take a paycut, if the deal is over 4-5 years.
Barcelona wouldn't say no to any offer over 100m. If Messi is pressing them, they'll probably negotiate lower. If he threatens them but leaves the money on the table, they could even let him go for free.
If Suning wants him and have the financial muscle to pull it off, then welcome Lionel Messi. If not, it was just a dream.