I generally stay mute on a lot of these posts about pricing due to the fact that there are so many things that need to be compared equally. One of the most difficult items to keep a price sheet on is ply. Plywood is much more difficult to compare than lumber. Numerous things to consider, A-1, A-2, A-3, A-4, B-2, B-3, B-4 plus all those in C and D grades. Cores, MDF, Poplar veneer, fir cores? Domestic or import? West coast manufacture or east coast? Is it a 1 time press where they lay up the cores, face and back veneers in 1 press or are they a calibrated core where the core is laid up, sanded then the face and back veneers laid up then sanded again. It all changes pricing. The competition for logs both plywood manufactures and sawmills have driven costs of poplar and maple quite high. I'm selling cherry to cabinet shops where they are painting it because it is cheaper than maple. That just shows the demand on particular products. Some distributors have higher operating costs than others. Next is a lot of manufactures have buyers on allocation right now. Columbia forest products is one. They can not produce what is being demanded and that brings the cost up, putting buyers on allocation on how much and how often they can buy drives costs up. Transportation costs have gone up so that has added to the costs. I typically buy $10-18k worth of ply a month and I struggle to get what I need due to availability. Every month I order ply the price has gone up to some degree or just isn't available. Some distributors may have a cheaper price since it was last months order they have in inventory and the other supplier might have just received a trailer load where the price has gone up.
If you are only needing a few sheets, try calling some cabinet shops to see if they have some over ordered material they would be willing to sell. Most shops only bring in what they need so that they do not have to carry inventory. Inventory is very expensive. Money out the door instantly and then waiting for buyers to replenish it.