Sad times! If you're mechanically minded and have the time, it might be worth taking the head off and checking the valves yourself. if they prove to be bent as mentioned you can consider buying a new head or sourcing a second hand head and fitting it yourself. Or if you really fancy it... you could replace the valves etc and do a head rebuild. Either way you are going to need to factor in, all the gaskets, studs, cam chain, cambelt all those other jobs and parts that go with it as a whole. which will work out rather costly! in which case you could maybe look at the complete used engine option. But with that, you'll at some point or straight away need to change the cambelt, cam chain etc causing even more cost.
I suppose the main question before you do anything is.. how did it happen. Is the cambelt still intact? Was it checked to see if it was out by a few teeth or still timed up? Or did the cam chain side fail?
if it turns out to be a jumped cambelt, you could consider going for the above head replacement route, hoping and assuming when the head is take off the valves are a little bent and no damage appears to have been done to the pistons. If you're not willing to take it on.. you could maybe get a garage to fit a head. I have only mentioned used items as not sure what "keep the cost down" entails. Unfortunately, whichever route you decide to go down with this situation is going to work out expensive. Shear bad luck and im sorry to hear it.