So I just finished The Showroom award and this was the list I came up with.
TLDR: If you just order 30 Elegy RH8s and can store them all, you should get the award.
Properties
You need three properties with 10 car garages to store all 30 cars. The three cheapest properties with 10 car garages are:
- 1623 South Shambles St - Garage - 105,000
- 1337 Exceptionalist Way - Garage - 112,500
- Unit 76 Greenwich Parkway - Garage - 120,000
Property total just garages: 337,500
I'm going to assume that someone would want at least one high rise apartment in order to do Heists and other things. So instead of the most expensive garage, you'd buy the cheapest 10 car apartment:
- 1623 South Shambles St - Garage - 105,000
- 1337 Exceptionalist Way - Garage - 112,500
- Del Perro Heights, Apt 7 - Apartment - 200,000
Property with apartment: 417,500
Cars
You need 30 cars total and I see 3 different sources for getting these cars.
One source is getting Elegy RH8s which are free on consoles if you sign up for the social club. Plus, they already count as "modded" which will help in the next section. Unfortunately, if you are on PC, they cost 95,000 and the total will jump up to 2,850,000.
The other two options are stealing cars or buying Karin Rebels.
Mods
If you have Elegy RH8s you won't have to buy any mods and you are done. If you steal cars or buy Rebels, then you'll have to mod every single car. The cheapest mod I could find across cars that makes sure there's a cosmetic change was the Exhaust. It seemed like the cheapest Exhaust mod was usually $750.
- Got Elegy RH8s - 30*0 = 0
- Modding cars with Exhaust - 30*750 - 22,500
Total
So assuming that you have no 10 car properties already and no cars, the absolute cheapest to get with 3 10 car garages and Elegy RH8s on consoles would be 337,500. This money would be completely spent on the garages. The most expensive if you just buy 30 Karin Rebels, Exhausts, and get the cheapest 10 car apartment would be 530,000.