Negotiation without offending

I've been surveying for suppliers for a company that I'm starting. I have a little experience in the field, and know some existing good ones, but decided to check and see if I could find some cheaper supplies.

I'd rather not say what supplies these are exactly, but they're very important to the business model. Along the lines of the meat in a burger or gold in a jewelry factory. I make a good profit margin on them (around 60%), but because they form much of the product, even a slightly lower cost will improve the profit margin.

When asked about the price I was willing to pay, I mentioned a price just slightly lower than what I paid for some similar supplies. They gave me a free sample, and I find the quality to be way higher than what I was using previously. In fact, the quality is high enough to match against my best competitors, and in all honesty, I'd gladly pay 50% more than what they're asking.

The supplies I was using before this was also obtained from a reseller, and not directly from the manufacturer. The supplies I plan to get is almost directly from the manufacturer. I don't think I'm being greedy, because even with a lower price, they're still making a very high profit margin.

So, my question is, what is the best way to negotiate for a lower price without offending them? I don't want to trick or con them into thinking that it's a good deal and later on have them decide that it's not. I'm already very excited to buy from them, and want to maintain a good long-term relationship.

I agree with the comment of Steve Jones. In top of that, I would say that the whole "business" is about negotiating, trying to buy as cheap as possible and to sell as expensive as possible. That is just a part of the game. By negotiating, you are not offending them (just pay attention to some cultural aspects). They know their margins and they want to make business, same as you. So it's simple: they accept what they accept - it's not really your problem. As it is not their problem to know what is your margin.

The reason of the negotiation is to find conditions that suits all the involved parties. So don't worry about the negotiation - if both want to do business, they will always find an agreement... Or they will change the client/supplier. Taht's business.

Name your price, but also listen to their price and reasons for their price. As you say, it's higher quality, so if they know it, they might ask for more. I have seen companies that refuse to negotiate with people and make exactly 0$ from them while competition makes over 20k per year from that same client. So stubborn companies exist, but most will be ready to hear you out. Lower prices usually means you have to buy more though, so be ready for that. There are other practices too that you need to be ready to accept like for example:

The car tire cartel will always negotiate 10%-20% from their price if you are a major distributor, but if they do that, they lock you into selling at the suggested retail price, whereas smaller distributors are told not to piss off their big clients (which is why most prices for tires are the same give or take 10$ (per tire)).

The construction industry separates by region the work they get from the government and predetermine each other's bids every time to share the profits. So they work with the suppliers to make sure new competition doesn't come in, therefor, if you buy wood from a certain place, they basically forbid you to bid on public contracts and give you the lower prices.