It's not that simple. You search for a title sponsor. That is the one that defines the overall budget. Jumbo is a very good one, but how many like Jumbo do you have, in Europe? Not that much. PL has to do with the highest bidding title sponsor. He can't just add more title sponsors (or the very definition of title sponsor is compromised, and that only works if all of your sponsors are OK with that, but then you end up like Giocattoli-Androni), so he needs:
- a title sponsor
- a second sponsor
additional sponsors for everything else.
If you can't get a title sponsor (in PL's case: in Belgium) that isn't willing to pay 5 million
more per year and thus a second sponsor that is willing to pay 2 million
more (the difference between QS and Jumbo is 7 million), you simply start the season with 7 million less than a team like Jumbo (not even talking about UAE and Ineos).
And while QS has an average budget, you need a top 5 budget to pay top 5 stars. If you have 7 million more to play with, you can overbid QS for any top 5 salary rider with (easily) a million. In a market where top riders get paid around 3-5 million, that extra million is all it takes to loose out on that 1-5 crucial transfers you need. And if you're Ineos, you can simply pick away ANY rider, and even buy a rider still on a contract by paying the fine.
The only reason QS (and other average budget teams) are still having a roster with talented riders, is the fact that even top teams have limited spaces in their roster, and some riders are rather willing to ride their own program / be a protected rider, for less money, than just cash in at Ineos.