You can drop more than that, Plus is an annual contract and there are revenue factors.
You should reach out to your contact from Plus sales department.
Otherwise to get access to Multi-Pass employ an agency, or shopify Partner|Expert|Plus-Partner|Plus-Expert,etc to go through the discovery with you.
I see this all the time so I recommend reflecting on the scale and approach as a business process.
If it's critical and dropping $2000 for a test makes you blanch then moving to enterprise is likely to be premature, be sure you've exhausted other options.
If your first action wasnt' to reach out directly to enterprise level support it is very important to ask yourself why.
Really just wondering if there is some kind of free trial or test mode, which I think many devs would expect for something like this. It's kinda prohibitive to have to pay $2000 just to START developing this feature into our store. What if it doesn't work out/we realize something won't work with our setup once we get into the details of writing the code?
If you have a partner account or are working with a partner and they cannot enable this in a dev store then reach out through the partner dashboard.
Have you gone over the docs? What aspect do you think could fail to work for you?
Definitely search the whole forum for common multipass cases and issues
Make sure to review the example implementations in the docs and the third party one for nodejs https://github.com/beaucoo/multipassify
and remember passing customer tags overwrites tags