If the price includes cross drilling and injecting, it is a good price. Crack repair is not as easy as stuffing epoxy into the crack. Preperation of the crack is very important.

Ask for references and a warranty. Make sure the epoxy he is using has expansion/contraction properties above 15%.

If you do it yourself and do a poor job, it will cost you more to have your application removed and the crack resealed.

Regarding the cost. It may seem like a lot, but running a business is expensive. Associated costs are quite high and an honest contractor needs to make so much money a day to keep the business running.

Also, epoxy injecting equipment and the epoxy is expensive.

I have found the cross drilling method to be one of the best methods. It allows the epoxy to get deeper into the wall, where it needs to be. Just injecting into a small crack may only enter an inch or less into the crack. Also, you need to have proper termination of the crack in order to keep the crack from migrating.

MHO - Pay a professional.