```python
from fastapi import FastAPI, Query
import helpers
import asyncio

app = FastAPI()


@app.get("/portfolio")
async def portfolio(symbols: str = Query(...)):
    sym_list = [s for s in symbols.split(",") if s]
    prices = await asyncio.gather(*(helpers.afetch_price(s) for s in sym_list))
    return {"prices": dict(zip(sym_list, prices))}
```