1. Tickets are on sale from the booking office.
(Does it mean that we can get the tickets at a reduced price?)
2. The new model goes on sale next month.
(Does this sentence mean that the new model will be sold at a reduced price next monthe?)
No. I said "on sale" USUALLY might mean at a reduced price. Not always. In these instances, it just means that the tickets or the car will be available next month or on a certain date, or at a certain place. In these instances, "for sale" and "on sale" are synonymous.
It can be confusing, I know.
The meaning must be derived from the context. For example, I cannot yet buy tickets for a hit musical that will play next fall. Season ticket holders may buy season tickets for several plays now, but individual seats will not go "on sale" until a later date. But an advertisement in today's newspaper says: "Cole Hardware Hardware Hot Deals: Sale Prices Valid Through April 30, 2016"
The tickets will not be at reduced price. The items listed in the advertisement are at "sale" or reduced prices.
The phrase "on sale" refers specifically to the availability for purchase, rather than suggesting a reduced price.
1. "Tickets are on sale from the booking office" means that the tickets are now available for purchase at the booking office. It does not indicate any information about the price. To determine whether the tickets are being sold at a reduced price, you would need to inquire specifically about any discounts or promotions related to the tickets.
2. "The new model goes on sale next month" means that the new model will be available for purchase next month. Again, it does not imply any information about the price. If you want to know if the new model will be sold at a reduced price, you would need to check with the seller or manufacturer for any promotional offers or discounts that may be applicable.