Working with a single price list is not realistic in the glass trade. A customer buying in bulk and a customer buying one piece do not pay the same figure; the price given to a dealer differs from the one given to an end user. That difference is the business model itself, not an inconsistency to be corrected.
The problem is not the difference but where it is kept. When prices are held in someone's head, or remembered by looking at old quotations, giving the same customer two different figures becomes unavoidable, and it usually surfaces when the customer lays two quotations side by side.
At this point the job of a glass pricing system is plain: hold more than one list and write down which list was used. While a quotation is prepared the customer's list is selected and the price comes from there. Later, when someone asks where that price came from, the answer sits on the record.
Updating a list is easy for the same reason. The product definition and the price do not live in the same place: products are in a shared catalogue, prices belong to the business. When only the price changes there is no need to review the whole catalogue. Your own buying and selling prices are visible only to you.
Old quotations are protected as well. When the price list is updated past quotations do not change; they keep carrying the price of the day they were issued. That looks like a small detail until a customer puts a three month old quotation in front of you, and the record is the only defence.
It is worth remembering that the price is not only the glass. Edging, tempering, holes and similar processes are added onto the line and change the total. When those charges stand as separate rows the customer sees what they are paying for; melted into a single total, the price becomes open to haggling.
The rest of the chain feeds from the same record. A glass quotation system takes the price from the list, a customer account system derives the balance from the order, and a costing system shows what sits underneath that amount. When looking for a quotation system for glass workshops, what to check is whether all four speak the same number.