They are available. Seats for team or enterprise plans cost more than the retail prices, but they are fixed prices with resetting usage limits. You can assign seats to members that are the equivalent of $20/$100/$200/mo plans.
You can also do everything metered. There are multiple ways to buy.
Who is selling these with enterprise trappings? What you're describing evaporated 2+ months ago. Everything is metered for enterprise users now. If there happens to be a stray vendor offering this I'd wager 2 things. 1) it's about to be phased out. 2) model limits will be in place so even that $200 plan won't go very far.