no I could get them cheap. $19/each for a 7 AH 12 V battery was astonishingly good, so $75 for 36Volts. The equivalent Lithium one would have been $600+ and I would have still needed a charger and a new BMS.
SLA is pretty idiotproof when it comes to charging.
I made a three-way harness to charge all three batteries at 12V with a car charger. Did that about 4 times a year. Normal charges were at 36V with no wiring changes needed.