```python
from fastapi import FastAPI, Query
from fastapi.responses import JSONResponse

import helpers  # noqa: F401

app = FastAPI()


@app.get("/portfolio")
async def get_portfolio(symbols: str = Query(...)):
    symbol_list = [s.strip() for s in symbols.split(",") if s.strip()]
    prices_coros = [helpers.afetch_price(symbol) for symbol in symbol_list]
    prices_list = await helpers.asyncio.gather(*prices_coros)
    prices_dict = dict(zip(symbol_list, prices_list))
    return JSONResponse(content={"prices": prices_dict}, status_code=200)
```