BofA/ML appears to have default limits of $15k/day for wealth management clients, and $25k/day for private bank clients, though there is a footnote stating that limits may actually be higher depending on the client. So at least for BofA/ML, they seem to essentially make higher transfer limits dependent on how much you're paying them in management fees.
The highest available limit I can find is $5,000 per day, and that's limited to private clients and businesses:
https://www.gobankingrates.com/banking/mobile/zelle-limits/
Common limits vary between $500 and $2,500 as you can see.
I've never heard of anyone being able to use it to send $10K in a single transaction, so it would be very helpful to know where you can do that.