When switching from T-Mobile to AT&T, AT&T will give you up to $650 in trade in credits. You must bring your current phone and number to AT&T and start a service plan to have the up to $650 credit applied when purchasing a new phone or covering early termination fees from T-Mobile. You must also trade-in your existing smartphone.
Included here are search results for available options when purchasing the LG V10 - click the link to compare All LG V10 Options.
Selecting different ways to pay - such as monthly installments, early upgrade or lease will make that hefty upfront cost evenly divided into a 24-month payment plan.
The amount of credit depends on the phone you are trading in. It depends on the model and condition of the device. You can receive anywhere between $0-$650.
As of April 2016...
If you were to purchase this phone outright from AT&T, it would cost you $719.99 upfront plus taxes and the monthly plan would cost you $55 a month.
If you were to purchase this phone through installments from AT&T, it would cost you $230 upfront plus taxes and the plan plus phone would cost you $72.50 a month.
These prices are also without your trade in credit.