Yea Plinko's odds are a bit misleading. I, like most people, thought that the 1000x is 1000:1 odds like 1000x in Crash (0.099%) but in fact it's 0.0015% which equals 66,666:1. Yet, there's 1 on both sides, so those odds are cut in half at 33,333:1, so it would take an average of 30,000 rolls to get it.
It's not a good idea to expect that during a session. Sometimes a mod in main chat will hold a rollhunt for it and I will try but more often than not I will have spent 15,000 rolls on it to no avail... I have gotten lucky a couple times too.
There is a counter-balance to those high odds though. The partial wins in everything in between, so it's not like other games where "losing" thousands of rolls takes a hard hit to your balance, you can often break even after all those rolls until you hit one. Don't forget there is a custom option too which is awesome. Create a table with whatever fits your betting goals. You can increase the 130x to 200x, 26x to 50x, etc. but whatever changes you make, the RTP (return to player) cannot be greater than 99% so you'd have to lower some other slots.