In my experience, the upgrade pricing always leaves you worse off than if you had bought Business from the beginning, especially if it is a multi-leg flight (since the later upgrade is per leg). I would only consider it if someone else had paid for the Economy fare and I would just pay for the actual upgrade. Paying for both makes no sense.

Our corporate travel policy requires all bookings to go through our travel agent and Swiss has traditionally not allowed me to upgrade TA bookings using Swiss Choice, only as per fare rules, which has then made even less sense price-wise.

Lufthansa are more flexible in terms of upgrade options.