I'm sure some restaurants do actually make proper birria but there is no chance they can afford to pay rent and also offer it for $1.50 a taco like someone whose only expense is materials and labor (and not commercial rent), so I haven't even seen anywhere make a go at this market at this pricepoint. One place I do like for tacos that is a restaurant is itself very barebones, a walkup only shack of a building situated in the parking lot of a liqour store that doesn't have any indoor space except for the small kitchen, and they charge accordingly more than a comparable street vendor (more like $2.50 a taco). This is probably the floor of what a brick and mortar can afford to charge for that tier of meat with involved prep.