Megabucks type machines hit fairly frequently as do other progressives like Jeopardy, Wheel of Fortune, Quartemania and Fabulous 50's. (There are also Nickel and Penny progressives)

These are what they call systems machines. In most jurisdictions these machines are linked together between all the participating casinos and are managed by IGT (International Gaming Technology) which not only owns the machines (These machines can only be rented not purchased usually at the cost of around $300 a day) but also is responsible for the payout of the Jackpot.
In these progressive machines, the jackpot payout does not come from the casino. It comes from IGT

In addition, if one were to read the fine print one would discover that the jackpot is paid out as a 20 year annuity.

It is for that reason that these are usually the lowest percentage payout machines in the casino as a portion of the monies wagered goes into the jackpot, some to pay for rental and the balance for profit