flint's point about timeline is the one that decides whether the fee is real. Luxury end buyers do longer diligence, so your contract has to survive weeks rather than days, and that changes what you negotiate at signing. A short earnest money deposit and a wide-open inspection contingency, which is standard practice in low-price wholesaling, reads as unserious to a seller with a $2m asset and often to their attorney.
So you're usually asked to put up real money. If the deposit at that level is 1% to 2% of price, you're risking $20k to $50k of your own capital on a deal you don't yet have a buyer for. That's the actual barrier, not the sourcing.
On the assignment itself, whether you can assign at all depends on the contract language and on state law, and a number of states have added disclosure or registration requirements around wholesaling that apply regardless of deal size. Confirm how your state treats it with a real estate attorney in that state before you sign anything at this price point, because a large visible transaction is the kind that gets examined.
One thing that goes wrong specifically at this level: your seller is more likely to be represented, and a listing agent who spots an assignment coming may push for a clause barring it or insist on a double close instead. A double close means you actually buy, which means transactional funding and two sets of closing costs and transfer taxes, and transfer taxes vary by state and can be substantial on a $2m sale. That can eat a third of a spread you thought was clean.