Ciao Judi,
Donna unfortunately linked the wrong blog posts. This is the one that describes the new pricing system for the Uffizi starting March 1, 2018:
https://www.visitflorence.com/blog/new-tickets-pricing-uffizi-gallery-museums/
In short, yes, the cost of the ticket has changed this year - the Uffizi Galleries (Pitti Palace, Uffizi museum, Boboli gardens) all have seasonal tickets now. From March to November, tickets will cost more, less in the other months. €20 is the full cost for visiting during "high" season if you pay at the gate there, waiting in line; pre-booking tickets adds 4 euro to the cost of the ticket if booked by phone and on the official site, more on other sites.
To be honest, I would usually recommend you book for that period as the museum is almost always busy from April onward (explains the "high" season ticket increase since the museum wants to increase revenue from those busy months) but we don't know whether the higher ticket might discourage some groups from visiting. So we have to see how the crowds at the museum are this spring and summer to see whether it has an effect or not.
I would recommend you book the ticket by phone (call +39-055-294-883, keeping in mind time differences - read
this page for times for the call center) and in this way you don't pay ahead of time, only when you pick up your ticket.
If you arrive and see short lines at the normal entrance (door #2), you could theoretically not pick up the pre-booked ticket (if you haven't paid for it, who can chase you down to pay for it?) and just pay the "at the door" ticket of €20. If the lines are long, you pick up your reserved ticket and pay the extra euros to skip the line ;-).
As a side note, Donna did link to more recent news that your Uffizi ticket will allow you to visit the
MAF (the archeological museum) for free -- so keep your Uffizi ticket to use it again!