I’m trying to make a smart booking decision with one of the Lufthansa Group airlines — Lufthansa, SWISS, Austrian Airlines, or Brussels Airlines — and I’d appreciate any advice.

I’m deciding between:

1. Booking a business class ticket directly
   
2. Booking economy class and then placing a Plusgrade bid for an upgrade to business
   

The problem is: I can’t see the minimum upgrade bid until after I book an economy ticket. That makes it hard to compare the total cost of both options before committing.
What I’d really like help with:
Are there any tools, tips, or strategies to estimate whether it will be cheaper to book business class directly, or to go with economy and bid for an upgrade through Plusgrade?

I'm not looking for exact numbers — I just want to know how others approach this kind of decision before purchasing, since I can't see the bid range in advance.