I agree with SoulSingerSonia 1000%. You are defeating the purpose by using conventional lemons during a cleanse. They are full of pesticides and other chemicals and you're not really getting the full benefit of the cleanse. As your body releases toxins, you're simply bringing more in.
To help with expenses, try shopping at farmer's markets and talk to the produce manager at your local natural food store or even whole foods about getting them in bulk and reducing your costs. You can sometimes find organic lemons and limes at Costco at reduced prices. Regarding the farmer's markets most of the time even if they're aren't labeled "organic", you know they are farmed without poisonous substances. Sometimes the stores have sales. Lemons are coming into season so the prices should go down???? Hopefully. Also check with your neighbors - most people who have fruit trees don't harvest them! And the poor fruit falls to the ground and rots. What a waste. It would be better to eat fruit from these trees than to buy conventional produce as well. I would say if you're really strapped financially and cannot afford organic, then it would probably be good to purchase the conventional fruit and cleanse. You will get some benefit from the cleanse, but you will get a better cleanse with organic lemons or limes. Just my opinion.
I've been eating organic produce for 15 years and yes it's a little more costly than conventional produce, but I feel I'm worth it and I adjust my budget accordingly. Aren't you worth it too?! We pay for quality items in other areas of our lives, why not make an investment in your health? There is a big difference in organic vs conventional produce - HUGE. Another way to look at it -- doctor's visits, chronic/terminal illness surgery, therapy & treatment etc are also very costly. Sometimes in the million/billion dollar range depending on the imbalance and illness. Why not put the money into yourself and enjoy your good health instead? Buy organic.