It is true that the maximum allowable deductible is higher because of the annual changes Medicare made to allowed deductible and out of pocket cap - but plans are permitted to set lower deductibles and lower out-of-pocket caps if they choose. Generally, it is not worth it because the premiums for plans with low deductibles are so much higher.
Also, if you shop carefully next October-December, when it is time to choose a new plan, you may be able to find one which does not require you to pay a deductible at all for the drugs you need. In most of the plans I've had, only about half of my meds are subject to the deductible.
Finally, as others have pointed out the maximum you can be charged during the entire year is $2100. The Medicare Prescription Payment Plan allows you to spread the costs out over the year, so you don't have to pay a ton of money in the first few months of the year and nothing at the end of the year. (That would let you get your 3 month supply - and whatever other meds you need the first 3 months of the year for around $525 (perhaps less, depending on what the cost of all of your meds over the year is predicted to be))
Check GoodRx for Repatha. I don't know your dose, but the price around her is $239/2 sureclicks - just be aware if you buy it without insurance it does not count toward your annual out-of-pocket. For me, that doesn't matter - my spend is pretty low. But for my spouse it is better to bite the bullet and buy it with insurance, since her spend this year will be over $2100. You probably want to go to Medicare.gov, find your plan, enter (or access) all your meds and see what your annual drug costs are predicted to be before buying drugs off-plan.
(Note: You should have received this explanation back in November-ish from your drug plan, while you still had the opportunity to shop for a better deal. We change plans nearly every year, based on the plan changes. My spouse's plan went from $8/month to $64/month - so we switched to a $0/month plan - she is going to hit the $2100 cap anyway, so no point in paying extra in premiums just to shift when she pays it.)