Alice is right about the big names, but in my experience, you should definitely add Adorama and Focus Camera to your list. I've bought dozens of lenses over the years and sticking to authorized dealers is the only way to ensure you dont get stuck with a grey market paperweight if something breaks. A few tips from a long-time shooter:

• Stick to authorized Sony retailers. If the price is way lower than B&H, it is probably a scam or has no warranty.
• Look for bundles at Adorama. They often throw in a free filter or cleaning kit for the same price as the lens alone.
• Check the Sony EDU store if you have a student email, sometimes it stacks with Black Friday pricing. I am keeping my eyes on these for the sales:
• Sony FE 24-70mm f/2.8 GM II
• Sony FE 70-200mm f/2.8 GM OSS II
• Sony FE 50mm f/1.2 GM Ngl, I have seen too many people lose money on shady sites. Just be careful out there... the deals will be everywhere but the warranty is what actually matters.

The current state of seasonal sales is unfortunately not as good as expected. I have analyzed the price trends over the last few years and the actual savings are often quite marginal when you factor in the shipping risks. I had some significant issues with a delivery last season where the internal elements were loose upon arrival. This experience honestly reminds me of when I tried to plan a budget-friendly trip to the coast. I spent hours calculating the fuel costs and found a cheap motel that looked decent in the photos. When I arrived, the place was under renovation and the noise was so loud I couldnt even hear myself think. I ended up spending most of my time at this local aquarium instead. They had this one tank with a giant octopus that was surprisingly active. I watched that thing for nearly three hours while it tried to open a jar. Anyway lol sorry kinda went off topic there.

Check Amazon, B&H Photo Video for best deals.