I'd say there's a pretty good case under section 2-201 of the UCC (I assume that the tickets are goods under 2-105, since they are movable and identified at the time the alleged contract was formed; although the fact that seller doesn't know where the seats associated with the tickets will actually be at the time of formation might not make these tickets present goods, this isn't a problem under 2-105(2), since comment 2 explains that a contract for sale can extend to future or contingent goods). Section 2-201(1), the UCC statute of frauds, provides that for a contract for the sale of goods priced at $500 or more (which makes this contract within the statute, if buyer buys 2 or more tickets, no matter where the seats are) to be enforceable, there must be a writing signed by the defendant (here, the seller). Though one might doubt whether email is a signed writing for the purposes of the statute, the comments put that to rest, since comment 1 paragraph 3 makes clear that to be "signed" means any authentication which identifies the party to be charged (see also 1-201, comment 39). The section also makes clear that the contract is enforceable even if the writing leaves out terms, or misstates them, or leaves terms open, including price; the only essential term is quantity, and the contract is only enforceable up to the quantity listed in the writing (in this case, the email). Thus, the statute of frauds does not preclude enforceability. Even if it did, one could make a reliance argument on behalf of buyer IF he could no longer secure tickets from someone else (without this, I'm not sure that his position has really changed that much, since otherwise he could just buy the tickets elsewhere), since he turned down offers to buy tickets from others.
All the other requirements needed for a contract seem to be in place: offer, acceptance, consideration (even though they didn't agree at the time on exactly what it would be, this doesn't matter, since the UCC provides for the filling in of open terms, including price, see sections 2-204, 2-206, 2-207, and 2-305).
Thus, I agree, there shouldn't be too much trouble in enforcing this contract.