Hello,
The valuation of your business depends on your ability to make a profit and your rate of growth. At one extreme end, a business with a very high rate of growth (%20) a month, can get away with no profits as in the world of startups.
On the other end, a business that is making a profit, with %0 year of year growth is not investable so is valued very low.

The other thing, I don't think it is fair to look at Uber as an "agency model". This way of thinking would be to miss the point on where & how they create value and thus are valued commercially.

There are multiple ways to do valuation. It takes into consideration the business sector as well. In case of commission in other word the revenue in your case, you can try the following models which are widely used. A) Revenue multiples B) Traffic Multiples C) Earning Multiples D) DCF analysis and E) GMV
In recent times, we are seeing a more significant number of early stage e commerce startups presenting their valuation based on GMV. But the biggest limitation of GMV is that it is based on gross orders and does not account for adjustments like returns, discounts, rebate, cancellations and cashbacks. It is not ideal to set a benchmark on GMV multiples as it highly depends on your business model. GMV often can be skewed by product mix and offers no insight into the value of the business.

Multiples of earnings – The “multiple earnings” approach uses an established market based Price/Earnings (P/E) Ratio (also known as PER) and is suitable for those businesses with a record of profit generation. It involves multiplying adjusted after tax profit by an industry sector related multiplier. In order to arrive at a meaningful post-tax profit figure, it will be necessary for certain adjustments to be made, which are known as “Normalising Adjustments”. The Valuer will need to scrutinise the accounts in order to establish if there were any income or expense items that were considered to be either of an extraordinary or non-recurring nature, or higher or lower than would be reasonably expected, in order to calculate maintainable profits. The normalising adjustments will be similar to those used with the EBITDA method below. Very often, the multiplier will be linked to quoted Companies listed in the Financial Times FTSE 100, 250 and AIM markets delivering broadly similar services to the business being valued but with a discount of between 30% to 70% applied for a non-quoted Company, usually depending on level of risk and transactional values for similar businesses sold. NB For smaller businesses, a more basic approach may used by some Valuers using a much lower multiple but based on PBT.
Earnings Before Interest, Tax, Depreciation & Amortisation (EBITDA) –