That would assure that the agent made more money, but whence would the pay distribution come? How would the travel agency collect more money for their placement of those lower-cost buys so they could share the "profits" with the salesperson? To equalize the incomes of both agency and agent, you might consider altering the formula to incent larger numbers of low-cost travel junkets. Lower fares are typically offered as inducements to encourage travel among those put off by costs, so all parties are hoping to break even through greater volume.
Maybe suggest different marketing techniques, like
- contacting proven veteran travellers to promote the unprecedented limited-time specially discounted offers
- focusing on carriage trade buyers for whom cost is no object who can now buy imperial packages for presidential prices
- cutting deals for group contracts with school or club or religious group tours.
Those are not technically "compensation" suggestions... even though they might produce the cash flow for appropriate incentive pools as the compensation output result.
Comp people should be business people first (and psychologists or economists second) in order to be reward specialists third.