Sustainable pricing design has several core principles. First, your pricing should cover the actual cost of services you provide, not just match competitors' prices downward. If what you provide includes technical support, samples, and customized spec services, these should all be factored into your pricing logic. Second, design different price structures for customers of different sizes or relationship depths—for example, set tiered pricing by purchase volume, offer stable fixed conditions for long-term partners, rather than killing the price on every deal. Third, keep quotation versions and conditions in written records so both sides clearly understand 'what the conditions are this time and what they will be next time', avoiding customers using the lowest price from last time as the starting point for further negotiation each time. This mechanism, combined with complete transaction records, lets you maintain a disciplined quotation system across different customers, rather than having a different approach for each deal with no traceable logic.