do you mind sharing your latest quote here to see if we can help to find ways to cut cost?
lots of the tunnel components do not need to be brand spanking new or the greatest of the greatest.
i recommend you shop around carwashconsignment or talkcarwash marketplace on facebook to see if there are parts you can buy cheaper.
otherwise, i would recommend budgeting for $500k. contractor works can be costly, and commercial electrician specializing in car wash can be a lot more expensive than you think unless the install team has one. i generally also recommend having reserve cash in case something goes wrong... and it will! at least around $30-50K.
i do recommend looking into ncs-macneil's z-frame. if your tunnel is 15ft wide, z-frame should barely fit:
here's one inside a gas station tunnel that's got a tight fit:
we use ncs-macneil in all our sites, and on top of my head if you bought everything brand new...
correlator $9k
conveyor $40k
pit grates $3k
double photo eye $2k
tape switch $400
cta $1.5k
z-frame $80K
5 10hp tech 21 dryers $30K
wheel brush $20K
tire shine $20k
wheel blaster $3k
air and water panel $10K
chemical board $30K
tunnel controller & board $20K
paystation $60K
motor control center $30k
2x utility arch $4k
chemical applicators and rainbars $5k
hydraulic power pack $10k
air compressor & dryer $20k
RO spot free $8k
shipping and handling would be like $20k, sales tax would be around $10k, install would be around $80k, contractor work for concrete and electrical $30K? so roughly around $600k if nothing goes wrong. if you try to scavenge for used items it'd be around $450-500K.
this is not counting other peripherals like grand entrance arch, inspection camera arch, tunnel cameras, high pressure prep guns, etc.
if you do go the mini tunnel route, i recommend retaining the staff you have to provide both exterior (via mini tunnel) and interior service so you would hit a different market from the express tunnel 2 miles away.