Is the Formula 1 Singapore Grand Prix really bringing in revenue for Singapore?

Yes, it is extremely worth it in my opinion.

And you can count on this government, with its penny-pinching ways to ensure it is value for money.

1. direct tourism spending. - Hotel occupancy rates are extremely high during F1 season, with some guests booking the rates for the next year season when they leave this year. You can ask those in the hotel industry, this period is peak working season. Same for all the retail, F&B serving tourists...
2. branding - "Singapore" appears on so many media. I was just browsing FOX sports channel when I was at work overseas, and there it is, 3 hours plus of F1, with the name Singapore appearing countless of time, and the showing of the view of the cities. This is quite an expensive air time and it helps reinforce business branding and the lure for people to consider visiting Singapore during the non-F1 season
3. Just like the movie Crazy Rich Asians, it reinforce the others' view of Singapore as a place where rich people hang out and where business deals are made. Not necessary felt by the public, but it helps in business a lot. People treat Singaporeans and Singapore as a business work place and it helps Singapore firms starting out overseas... this is something I feel that is difficult to calculate the value for.

And I believe the costs go down yearly as the government gets more and more efficient at setting up the venue year after year... bulk discounts? :D

It's a tough question, due to the complex nature of the spillover effects of an event like F1 into tourism, and many other multiplier effects.

On the baseline first, an F1 street race can cost between $40-60million to host. (All amounts in USD) This is purely for staffing, stands, road paving, insurance, etc.
There's then the licensing fees and all, because well, F1 teams need money to eat. In general, the F1 teams receive more than $1billion over the course of the year and 20 races. The actual licensing fee charged in Singapore is not known, but money comes from somewhere.

In the first race in 2008, the known statistic was that the race costs S$150million, and the Singapore government paid 60% of the bill. https://en.wikipedia.org/wiki/Singapore_Grand_Prix
Very fascinatingly, the total attendance is actually quite telling of the economic mood over the years, and the last 3 years it has actually risen.
So where do the other revenues come from? CESS is one of the more significant income sources for the government. During the F1 period, all gazetted businesses have to pay an additional 30% tax https://www.stb.gov.sg/content/dam/stb/document...
https://www.straitstimes.com/politics/parliamen...
Based on past collections, this is about $10-15 million a year. It's not stated if the Singapore government takes a share of the event promotor's profit, but let's assume it's no. Tickets can range from $200 to 1.5k for the 3-day event but note the expense of running such an event include the multiple concerts and what not https://f1destinations.com/the-definitive-ranki...
So tangibly, the Singapore government only makes perhaps $20million, out of an annual expenditure of $90 million. There are also multiple disruptions, and deployment of police, security, and spillover time wasted and inconvenience to people working around the area. But there's also the intangible benefits, such as increased brand recognition of Singapore as a tourism destination, potentially longer tourist trips who decide to stay after the F1 period, as well as baseline support for the economy.

To draw a parallel example, the public transport in Singapore is actually not a lucrative business. But you need the public transport business in order to have a sizable business so that you can venture into profitable spaces such as taxis, private charters, retail, advertisement, engineering services, etc. The way I see it, F1 helps increase the competency of Singapore companies, so that they gain the skillset to venture overseas to run similar events, or to grow their profits from other complementary areas.
Lastly, tourism receipts technically don't benefit the Singapore government directly, but it does help the businesses here get more revenue, and eventually, that helps create a more vibrant economy.
This might be a good read https://www.reuters.com/sponsored/article/ten-y...