Actually you can. When dealing with a pandemic causing the level of disruption we've seen, you throw money at propping up production of every serious vaccine candidate, hoping that at least one of them works out.
Every additional day of lockdown probably costs as much as the entire production lifecycle of a vaccine, including distribution.
I think the EU economy contracted at least 5% in 2020. The EU GDP was $18.3 tn, so 5% is about $915bn. That's $2.5bn per day (!). And that's just the direct impact, the whole psychological, PTSD, etc. longer term impact probably makes that higher, I'd be shocked if the total cost isn't something like $3bn per day.
They should have been throwing money at every reputable vaccine producer, including burning all red tape to make sure that excessive production capacity will be ready before the final approval is even given.
To be clear, I agree that the return on investment of a quick and successful vaccination campaign is so big that it makes sense to aggressively bet on it. But I also think the evidence shows we have bet quite aggressively on it, at least to unprecedented levels.
What I cannot comment on is how much better we could have done, the supply chain and logistics of producing 1 x (world population) for each candidate vaccine in the hopes at least one of them works and we can roll-it out quickly are so ridiculously complicated I don't know how it could have been made to work. I fear I would just be misdirecting my frustration with the current situation and an incomplete understanding of the problem from the comfort of my armchair.
My 81-year old grandparents will get their first dose of vaccine on February 28, while other countries are already vaccinating much younger people.