The best way to avoid this to simplify the interaction to a cost benefit choice. Offer the customers a choice of A for price Y or B for price Z. the customers will then focus on the price and the requirements and not the tech details.
When quoting price you should keep in mind the average customer will always take the lowest price. This means that you can lead them to make a good choice by balancing the price to push them that way. Also pricing should account for the doing, and the overhead (emails, calls especially if the customer keeps changing there mind.