It usually happens around this time of year, when the ocean water temperature drops below 60 degrees. Some surfers refuse to wear booties no matter what the water temperature might be, but most surfers are pragmatic.
Surf booties are the only socially acceptable surfing accessories, other than a wetsuit, that local surfers are allowed to wear to acknowledge the cold water, though there are surfing gloves and hoodies in most surf shops.
There are two basic booties. The split toe and rounded toe styles. Most surfers go with the split toe because it gives the them a little more feel of what the surfboard is doing. There are high-top and low-top booties. The low-top booties are mostly for surfing in warmer water where there are rocks. The high-top booties keep you warmer and protect you from the rocks.
For how much warmer booties keep your feet, the $35 is worth the expense. Everyday surfers keep two pairs, because putting on a cold wet bootie is, well, cold. My favorite reason for wearing booties is you do not feel the cold water when you first put in your foot. You will not even know how cold the water really is until it gets inside your wetsuit. Then you will know.