Is there a "subscription" involved with either Tom Tom GO 520 or 620?

My (very) old Tom Tom HOME device is no longer able to accept updates and Tom Tom has sent me an offer to upgrade to a GO 520 or GO 620 device. The offer has a price with the footnote "*based on current 1.5-yr subscription rate." What "subscription rate" is this? Is there a subscription fee for these devices? They're advertised on Amazon as having "lifetime maps".

(And I'm really hoping that these devices are a bit better than the ratings I see on Amazon which I take with a grain of salt lately).