600k for a corporate, if you can find one for sale. Around 200k downpayment to get going
430k for an individual, but you need a hack licence. Around 50k down payment to get going.
So to answer your question should you buy a medallion? If you got 200k, you can buy one but still can't drive it w/o the hack licence. If you have 55k, you can buy one, but still need the hack licence to drive it.
Its a good long term business. But you gotta deal with a lot of B/S. If you are serious about this business, you need a medallion eventually. There is no other value to this business but a medallion. Otherwise, you are just trading dollars for hours.