How do I stop guessing what to charge?

Write a ladder of round prices once (a list of allowed prices), then let orders move the price one rung (one step) at a time.

Shoup's idea: set the parking price by how many spaces are empty

Donald Shoup, a planning professor at UCLA (the University of California, Los Angeles), wrote The High Cost of Free Parking (2005, updated 2011) ¹². He proposes that cities charge fair market prices for parking on the street and spend the money on services in the neighborhoods where it is collected ¹. A 2003 ACCESS Magazine article states the test: lower the price when too many spaces are empty, raise it when too few are ³.

San Francisco, in the USA, tried that test on its parking meters. From August 2011 its transport agency, the San Francisco Municipal Transportation Agency (SFMTA), changed the hourly rate on each street block about every eight weeks, based on occupancy, the share of spaces holding a car ⁴.

Rates were not allowed above US$6.00 or below US$0.25 an hour. Over the two-year trial the agency made ten adjustments, and the average meter rate went from US$2.69 to US$2.58 ⁴.

The money stays in the neighborhood

Old Pasadena, a district of Pasadena, California, USA, had no parking meters until 1993, and its shop owners opposed them. The city offered to spend all the meter money in Old Pasadena, and the business owners and property owners agreed ³. In the 2001 financial year the district's 690 meters earned US$1.2 million after costs, and US$448,000 of it repaid a US$5 million loan for sidewalks and alleys ³.

A ladder in baht

A ladder is a list of prices that are allowed. The lowest is the floor, the highest is the ceiling. The price sits on one rung. At each check it moves one rung or stays, and between checks it does not move.

This example is made up for this column. A service has ten places a month (ten customers it can take), a ladder of ฿1,000, ฿1,200, ฿1,500, ฿2,000 and ฿2,500, and a starting price of ฿1,500.

From ฿2,500 the price cannot rise, and from ฿1,000 it cannot fall. Each step on this ladder changes the price by 20 to 33 percent.

A Thai ladder can use prices with nines. The Thailand Foundation says Thai numerology (beliefs about lucky numbers) counts nine, เก้า (kao), as the luckiest number, and links its sound to ก้าว (kao), "to move forward" ⁷.

Hongdam sets its prices by this rule

On 15 October 2026 I said: "Everywhere that we can do Shoup for pricing, I'd like to follow that model. It's a universal preference for me." For Hongdam I described it as "prices set by the market itself. Round or auspicious numbers, generous on both sides. Rarely determined by me." (Auspicious means lucky.)

Hongdam's price list states the rule ⁵. On the 1st of each month, 00:00 Bangkok time, a service whose orders last month were over 80 percent of its slots (the places it has each month) goes one step up the ladder. Under 60 percent, one step down. In between, no change. Each service stays between its own floor and ceiling. The list shows 1 December 2026 as the first check ⁵.

On a service card in Hongdam's shop a reader sees a row of bars, one bar for each rung from the low price to the high price, with the current rung marked. Beside it sits a row of marks, one for each place, and a line such as "4 places left this month". When opened, the card reads "Price now", "low", "high" and "Prices move with demand on the 1st of each month" ⁶. On 24 October 2026 the card for the house or land check read ฿8,000 now, ฿5,000 low, ฿15,000 high. Its six bars are the six rungs ฿5,000, ฿6,000, ฿8,000, ฿10,000, ฿12,000 and ฿15,000, taken from a single ladder of 36 numbers that runs from ฿10 to ฿200,000 ⁶.

Floors and ceilings differ by service. On the same day "Paper forms typed into a sheet" listed ten slots, a floor of ฿500, a ceiling of ฿2,000 and a price of ฿1,000 ⁵. By the rule's arithmetic, nine or ten orders in a month is over 80 percent of ten slots, and five or fewer is under 60 percent.

Hongdam also sells this pricing system. Its card Prices that follow demand sets prices for rooms, a menu, tickets or stock "the way San Francisco prices parking" ⁸.