I have a Ping brand lithium battery that a friend bought about 4 years ago that has been holding up really well and everyone that I've heard of who has used them has liked them, it also has a BMS built in to the pack.
48 Volt LiFePO4 Battery Packs with BMS (Battery Management System)
going with a 48V system is a good idea, I have a crystalite motor and ran it at 33v and it worked ok, but it's designed to work up to 72v with the correct controller, I kind of wish I had spent extra on a higher voltage controller but I didn't, 48v tho should give you plenty of speed and is a common voltage for everything else.
the $1,500 price range is why I choose that price point for my electric motorcycle, people are willing to spend that much on an electric bicycle, so why not a motorcycle?
On my E-bike, I found that I was drawing around 300 to 400 watts on flat to go 20mph without pedaling, or about 20 watt hours per mile, I'm 250lb's and had a lower voltage pack so I had a bit more line loss then you should see, but 15-20 watt hours per mile at 20mph seems pretty common and with your battery that would give you ~50 miles.